PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Part 9 – The Chat View & Mediator

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

The final mediator, and the final actor in our application. The job of the chat view is to popup a window where you receive and send message to another user. You should be able to open multiple chat windows at once, and each window is bound to a specific and unique JID.

I’m just going to present the code for this with a short explanation of anything odd rather than explicitly go through the steps. If you have trouble understanding anything go back to the previous sections on mediators and read them through again.

ChatView.mxml

   1: <?xml version="1.0" encoding="utf-8"?>
   2: <mx:TitleWindow xmlns:mx="http://www.adobe.com/2006/mxml" title="" showCloseButton="true">
   3:     <mx:Script>
   4:         <![CDATA[
   5:         import mx.formatters.DateFormatter;
   6:         import org.davekeen.xiffer.events.ChatEvent;
   7:         import org.jivesoftware.xiff.core.JID;
   8:         import org.jivesoftware.xiff.data.Message;
   9:
  10:         private var jid:JID;
  11:
  12:         /**
  13:          * The send button was clicked so dispatch an event to the mediator
  14:          */
  15:         private function sendClick():void {
  16:             var inputText:String = inputTextArea.text;
  17:
  18:             if (inputText && inputText.length > 0) {
  19:                 dispatchEvent(new ChatEvent(ChatEvent.SEND_MESSAGE, jid, inputText));
  20:                 inputTextArea.text = "";
  21:             }
  22:         }
  23:
  24:         public function setJID(jid:JID):void {
  25:             this.jid = jid;
  26:
  27:             title = jid.toBareJID();
  28:         }
  29:
  30:         public function getJID():JID {
  31:             return jid;
  32:         }
  33:
  34:         /**
  35:          * Format and add a message to the chat pane
  36:          * 
  37:          * @param    message
  38:          */
  39:         public function addMessage(message:Message):void {
  40:             var dateFormatter:DateFormatter = new DateFormatter();
  41:             dateFormatter.formatString = "HH:NN";
  42:             chatTextArea.text += "[" + dateFormatter.format(new Date()) + "] " + message.body + "n";
  43:         }
  44:
  45:         ]]>
  46:     </mx:Script>
  47:     <mx:VBox>
  48:         <mx:TextArea editable="false" width="270" height="200" id="chatTextArea" />
  49:         <mx:HBox>
  50:             <mx:TextArea width="210" height="40" id="inputTextArea" />
  51:             <mx:Button id="sendButton" width="50" height="40" label="Send" click="sendClick()" />
  52:         </mx:HBox>
  53:     </mx:VBox>
  54: </mx:TitleWindow>
  55:

ChatMediator.as

There is something slightly different about this view compared to the Login or Roster views. The chat windows are dynamically created when needed and thrown away when they are closed by the user so we can’t have a permanent view component as the viewComponent of ChatMediator.as. Instead we’ll pass the top level Application.mxml component since this is what’s required in the arguments of PopupManager.addPopup.

   1: /*
   2:  Mediator - PureMVC
   3:  */
   4: package org.davekeen.xiffer.view {
   5:     import flash.display.DisplayObject;
   6:     import flash.display.DisplayObjectContainer;
   7:     import flash.events.Event;
   8:     import mx.managers.PopUpManager;
   9:     import mx.managers.PopUpManagerChildList;
  10:     import org.davekeen.xiffer.ApplicationFacade;
  11:     import org.davekeen.xiffer.events.ChatEvent;
  12:     import org.jivesoftware.xiff.core.JID;
  13:     import org.jivesoftware.xiff.data.Message;
  14:     import org.puremvc.as3.interfaces.IMediator;
  15:     import org.puremvc.as3.interfaces.INotification;
  16:     import org.puremvc.as3.patterns.mediator.Mediator;
  17:     import org.davekeen.xiffer.view.*;
  18:     import org.davekeen.xiffer.view.components.ChatView;
  19:
  20:     /**
  21:      * Chat Mediator - controls and stewards all popup chat windows
  22:      */
  23:     public class ChatMediator extends Mediator implements IMediator {
  24:
  25:         // Cannonical name of the Mediator
  26:         public static const NAME:String = "ChatMediator";
  27:
  28:         /**
  29:          * An associative array of open ChatViews
  30:          */
  31:         private var chatViews:Array;
  32:
  33:         public function ChatMediator(viewComponent:Object) {
  34:             // pass the viewComponent to the superclass where 
  35:             // it will be stored in the inherited viewComponent property
  36:             super(NAME, viewComponent);
  37:
  38:             chatViews = new Array();
  39:         }
  40:
  41:         /**
  42:          * Get the Mediator name.
  43:          * <P>
  44:          * Called by the framework to get the name of this
  45:          * mediator. If there is only one instance, we may
  46:          * define it in a constant and return it here. If
  47:          * there are multiple instances, this method must
  48:          * return the unique name of this instance.</P>
  49:          * 
  50:          * @return String the Mediator name
  51:          */
  52:         override public function getMediatorName():String {
  53:             return ChatMediator.NAME;
  54:         }
  55:
  56:         /**
  57:          * List all notifications this Mediator is interested in.
  58:          * <P>
  59:          * Automatically called by the framework when the mediator
  60:          * is registered with the view.</P>
  61:          * 
  62:          * @return Array the list of Nofitication names
  63:          */
  64:         override public function listNotificationInterests():Array {
  65:             return [
  66:                     ApplicationFacade.OPEN_CHAT_WINDOW,
  67:                     ApplicationFacade.RECEIVE_MESSAGE,
  68:                     ApplicationFacade.VALID_LOGIN,
  69:                     ApplicationFacade.DISCONNECT
  70:                     ];
  71:         }
  72:
  73:         /**
  74:          * Handle all notifications this Mediator is interested in.
  75:          * <P>
  76:          * Called by the framework when a notification is sent that
  77:          * this mediator expressed an interest in when registered
  78:          * (see <code>listNotificationInterests</code>.</P>
  79:          * 
  80:          * @param INotification a notification 
  81:          */
  82:         override public function handleNotification(note:INotification):void {
  83:             switch (note.getName()) {
  84:                 case ApplicationFacade.OPEN_CHAT_WINDOW:
  85:                     var jid:JID = note.getBody() as JID;
  86:                     showChatWindow(jid);
  87:                     break;
  88:                 case ApplicationFacade.RECEIVE_MESSAGE:
  89:                     var message:Message = note.getBody() as Message;
  90:
  91:                     // Add the message to the view
  92:                     chatViews[message.from.toBareJID()].addMessage(message);
  93:                     break;
  94:                 case ApplicationFacade.VALID_LOGIN:
  95:                     // Enable all chat windows
  96:                     for each (var chatView:ChatView in chatViews)
  97:                         chatView.enabled = true;
  98:
  99:                     break;
 100:                 case ApplicationFacade.DISCONNECT:
 101:                     // Disable all chat windows
 102:                     for each (chatView in chatViews)
 103:                         chatView.enabled = false;
 104:
 105:                     break;
 106:                 default:
 107:                     break;
 108:             }
 109:         }
 110:
 111:         /**
 112:          * Open up a chat window for this particular JID
 113:          * 
 114:          * @param    jid
 115:          */
 116:         private function showChatWindow(jid:JID):void {
 117:             // If the window exists already don't do anything
 118:             if (!chatViews[jid.toBareJID()]) {
 119:                 var chatView:ChatView = new ChatView();
 120:
 121:                 PopUpManager.addPopUp(chatView, viewComponent as DisplayObjectContainer, false);
 122:                 PopUpManager.bringToFront(chatView);
 123:                 PopUpManager.centerPopUp(chatView);
 124:
 125:                 chatView.addEventListener(Event.CLOSE, onChatViewClose);
 126:                 chatView.addEventListener(ChatEvent.SEND_MESSAGE, onSendMessage);
 127:                 chatView.setJID(jid);
 128:
 129:                 // Add the chat view to the associative array
 130:                 chatViews[jid.toBareJID()] = chatView;
 131:             }
 132:         }
 133:
 134:         /**
 135:          * The user has typed a message and sent it
 136:          * 
 137:          * @param    chatEvent
 138:          */
 139:         private function onSendMessage(chatEvent:ChatEvent):void {
 140:             var chatView:ChatView = chatEvent.currentTarget as ChatView;
 141:
 142:             // Construct a XIFF message
 143:             var message:Message = new Message(chatEvent.getJID(), null, chatEvent.getMessage(), null, Message.CHAT_TYPE);
 144:
 145:             // Echo it to our own view
 146:             chatViews[chatView.getJID().toBareJID()].addMessage(message);
 147:
 148:             // And send off a notification
 149:             sendNotification(ApplicationFacade.SEND_MESSAGE, message);
 150:         }
 151:
 152:         /**
 153:          * The chat window has been closed
 154:          * 
 155:          * @param    event
 156:          */
 157:         private function onChatViewClose(event:Event):void {
 158:             var chatView:ChatView = event.currentTarget as ChatView;
 159:             chatView.removeEventListener(Event.CLOSE, onChatViewClose);
 160:             PopUpManager.removePopUp(chatView);
 161:
 162:             // Delete the chat view from the associative array
 163:             delete chatViews[chatView.getJID().toBareJID()];
 164:         }
 165:
 166:     }
 167: }

SendMessageCommand.as

   1: /*
   2: Simple Command - PureMVC
   3:  */
   4: package org.davekeen.xiffer.controller {
   5:     import org.davekeen.xiffer.events.ChatEvent;
   6:     import org.davekeen.xiffer.model.XMPPProxy;
   7:     import org.jivesoftware.xiff.data.Message;
   8:     import org.puremvc.as3.interfaces.INotification;
   9:     import org.puremvc.as3.patterns.command.SimpleCommand;
  10:     import org.puremvc.as3.patterns.observer.Notification;
  11:
  12:     /**
  13:      * Send a message to the proxy
  14:      */
  15:     public class SendMessageCommand extends SimpleCommand {
  16:
  17:         override public function execute(note:INotification):void {
  18:             var message:Message = note.getBody() as Message;
  19:             var xmppProxy:XMPPProxy = facade.retrieveProxy(XMPPProxy.NAME) as XMPPProxy;
  20:
  21:             // Send the message
  22:             xmppProxy.sendMessage(message);
  23:         }
  24:
  25:     }
  26: }

And there it is! A working Jabber, Flex and PureMVC application of your very own.

Let’s wrap it all up with a conclusion, a working demo and the full source code.

PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Part 8 – The Roster View & Mediator

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

By now you should be becoming a bit of an old hand at this PureMVC lark, so I’m going to be explaining stuff in a bit less detail.  If you get stuck re-read the previous sections until you have everything clear in your head.

The Roster is very simple.  We want a Flex DataGrid displaying usernames and login status and we need a ‘Start chat…’ button that opens a chat window.

In order to implement this view we’ll need a new event called ChatEvent.as.  The JID class is part of the XIFF framework and is used to identify a Jabber user.  The RosterView will only use START_CHAT, but we’ll need SEND_MESSAGE in the next and final view.

   1: package org.davekeen.xiffer.events {
   2:     import flash.events.Event;
   3:     import org.jivesoftware.xiff.core.JID;
   4:     
   5:     /**
   6:     * This event is related to the ChatViews
   7:     * 
   8:     * @author Dave Keen
   9:     */
  10:     public class ChatEvent extends Event {
  11:         
  12:         public static const START_CHAT:String = "start_chat";
  13:         public static const SEND_MESSAGE:String = "send_message";
  14:         
  15:         private var jid:JID;
  16:         private var message:String;
  17:         
  18:         public function ChatEvent(type:String, jid:JID, message:String = null, bubbles:Boolean=false, cancelable:Boolean=false) { 
  19:             super(type, bubbles, cancelable);
  20:             
  21:             this.jid = jid;
  22:             this.message = message;
  23:         } 
  24:         
  25:         public function getJID():JID {
  26:             return jid;
  27:         }
  28:         
  29:         public function getMessage():String {
  30:             return message;
  31:         }
  32:         
  33:         public override function clone():Event { 
  34:             return new ChatEvent(type, jid, message, bubbles, cancelable);
  35:         } 
  36:         
  37:     }
  38:     
  39: }

We’ll also need to define one new notification in ApplicationFacade.as called OPEN_CHAT_WINDOW:

   1: public static const OPEN_CHAT_WINDOW:String = "open_chat_window";

Next we create our RosterView.mxml file in components:

   1: <?xml version="1.0" encoding="utf-8"?>
   2: <mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml" xmlns="*" width="100%" height="100%">
   3:     <mx:Script>
   4:         <![CDATA[
   5:         import flash.events.Event;
   6:         import mx.events.ListEvent;
   7:         import org.davekeen.xiffer.events.ChatEvent;
   8:         import org.jivesoftware.xiff.core.JID;
   9:         
  10:         private function onChatClick():void {
  11:             if (rosterGrid.selectedItem) {
  12:                 // Get the selected item and convert it to a JID
  13:                 var jid:JID = new JID(rosterGrid.selectedItem.jid);
  14:                 
  15:                 // Dispatch an event for the mediator
  16:                 dispatchEvent(new ChatEvent(ChatEvent.START_CHAT, jid));
  17:             }
  18:         }
  19:         
  20:         ]]>
  21:     </mx:Script>
  22:     <mx:TitleWindow id="titleWindow" title="Buddy list" enabled="false">
  23:         <mx:DataGrid id="rosterGrid" editable="false" width="160" height="300" showHeaders="true">
  24:             <mx:columns>
  25:                 <mx:DataGridColumn dataField="displayName" headerText="Username" />
  26:                 <mx:DataGridColumn dataField="online" width="55" headerText="Online?" />
  27:             </mx:columns>
  28:         </mx:DataGrid>
  29:         <mx:Button width="160" label="Chat..." click="onChatClick()" />
  30:     </mx:TitleWindow>
  31: </mx:Canvas>

Add this component to the display list of our top-level Application.mxml component so that the <mx:Canvas> component now reads:

   1: <mx:Canvas left="0" top="0" right="0" bottom="0">
   2:     <view:LoginView id="loginView" />
   3:     <view:RosterView y="30" id="rosterView" />
   4: </mx:Canvas>

Now we need to create RosterMediator.as in the view folder, and register it with PureMVC.  Using the rule we applied in the previous section we can see that we need to do this registration in ApplicationMediator.as:

   1: public function ApplicationMediator(viewComponent:Object) {
   2:     // pass the viewComponent to the superclass where 
   3:     // it will be stored in the inherited viewComponent property
   4:     super(NAME, viewComponent);
   5:     
   6:     facade.registerMediator(new LoginMediator(application.loginView));
   7:     facade.registerMediator(new RosterMediator(application.rosterView));
   8: }

All that is left now is to configure our mediator using the same steps as in the previous section.

1. Add listeners

RosterView.mxml dispatches only ChatEvent.START_CHAT so let’s add a listener in the constructor:

   1: public function RosterMediator(viewComponent:Object) {
   2:     // pass the viewComponent to the superclass where 
   3:     // it will be stored in the inherited viewComponent property
   4:     super(NAME, viewComponent);
   5:     
   6:     rosterView.addEventListener(ChatEvent.START_CHAT, onStartChat);
   7: }
   8:  
   9: private function onStartChat(chatEvent:ChatEvent):void { }

2. Add notifications

The Roster window need to enable and disable depending on whether or not the user is connected to a jabber server, and also needs to fill in the DataGrid with the list of buddies.  To achieve these goals the mediator will need to register an interest in ApplicationFacade.VALID_LOGIN and ApplicationFacade.DISCONNECT.

   1: override public function listNotificationInterests():Array {
   2:     return [
   3:             ApplicationFacade.VALID_LOGIN,
   4:             ApplicationFacade.DISCONNECT
   5:             ];
   6: }

And here are the clauses for the switch statement:

   1: override public function handleNotification(note:INotification):void {
   2:     switch (note.getName()) {
   3:         case ApplicationFacade.VALID_LOGIN:
   4:              break;
   5:         case ApplicationFacade.DISCONNECT:
   6:             break;
   7:         default:
   8:             break;        
   9:     }
  10: }

3. Fill in the event listeners and switch clauses

Firstly we’ll fill in the onStartChat event listener.  This will very simply send an ApplicationFacade.OPEN_CHAT_WINDOW with the JID as the argument.  Although we could have passed the ChatEvent itself as a parameter in this case there is no need to use a value object as to open a chat window we only require a single item of information – the JID.

   1: private function onStartChat(chatEvent:ChatEvent):void {
   2:     sendNotification(ApplicationFacade.OPEN_CHAT_WINDOW, chatEvent.getJID());
   3: }

You’ll notice that the ApplicationFacade.OPEN_CHAT_WINDOW notification is not mapped to a command – this is because the only responder to the notification will be the ChatMediator that we are about to create in the next section so there is no need to have a command.  However, one of the beautiful things about PureMVC is that if it turned out later in the development that this notification needed to affect the model in some way we could implement this merely by adding a new command and registering it, and there will be no need to make any changes to the rest of the application.

Compile and run the application and enjoy the working buddy list!  Only one view left to go…

PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Part 7 – The Login View & Mediator

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

In this part of the tutorial we’ll create the login bar, and by the end of this section our application will be able to connect to any XMPP server with a username & password!

In the components package create a new MXML file name LoginView.mxml and in the view package create a new mediator called LoginMediator.as using Add->New Mediator… (if you don’t see this menu item be sure you’ve installed the PureMVC FlashDevelop templates from PureMVC: First thoughts & FlashDevelop templates correctly).

As we explained in the previous section add a helper method to the LoginMediator to cast the viewComponent:

   1: private function get loginView():LoginView {
   2:     return viewComponent as LoginView;
   3: }

Note that in order to get the application to compile you’ll need to explicitly import the LoginView using:

   1: import org.davekeen.xiffer.view.components.LoginView;

Now we want to add the LoginView to the display list by including it in Application.mxml (giving it an id of loginView so we can reference it from the mediator).  Add this MXML within the <mx:Application> tag (stick it at the end just before </mx:Application>):

   1: <mx:Canvas left="0" top="0" right="0" bottom="0">
   2:     <view:LoginView id="loginView" />
   3: </mx:Canvas>

Now we need to register our mediator with PureMVC.  Now this point is important to understand as it seems to confuse  – since LoginView is a sub-component of Application we need to register the view within the Application’s mediator.  This can be made into a general rule:

  • If the mediator you are registering heralds the top level component (i.e. Application.mxml) register it in StartupCommand.
  • If the mediator you are registering heralds a child of another component register it in the constructor of that component’s mediator.

Just to confuse things I’d better point out that this rule doesn’t apply in quite the same way if you are dynamically creating and removing mediators, but we’ll save that for another tutorial.

Anyway, the upshot of all that is that we call registerMediator in the constructor of ApplicationMediator:

   1: public function ApplicationMediator(viewComponent:Object) {
   2:     // pass the viewComponent to the superclass where 
   3:     // it will be stored in the inherited viewComponent property
   4:     super(NAME, viewComponent);
   5:     
   6:     facade.registerMediator(new LoginMediator(application.loginView));
   7: }

Here is the code for LoginView.mxml.  As this is a PureMVC tutorial, not a Flex one, I’m not going to go in any detail about how it works, but these are the only things you need to care about:

  • When the user clicks ‘Connect’ it dispatches a LoginViewEvent.LOGIN event containing the username, password and server.
  • When the user clicks ‘DIsconnect’ it dispatches a LoginViewEvent.LOGOUT event.
  • It exposes a showInvalidLoginAlert() method that pops up a ‘Invalid username/password’ window.
   1: <?xml version="1.0" encoding="utf-8"?>
   2: <mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml" xmlns="*" width="100%" height="100%">
   3:     <mx:Script>
   4:         <![CDATA[
   5:         import mx.controls.Alert;
   6:         import org.davekeen.xiffer.events.LoginViewEvent;
   7:         
   8:         /**
   9:          * Dispatch a connect event to the mediator
  10:          */
  11:         private function onConnectClick():void {
  12:             dispatchEvent(new LoginViewEvent(LoginViewEvent.LOGIN, usernameTextInput.text, passwordTextInput.text, serverComboBox.text));
  13:         }
  14:         
  15:         /**
  16:          * Dispatch a disconnect event to the mediator
  17:          */
  18:         private function onDisconnectClick():void {
  19:             dispatchEvent(new LoginViewEvent(LoginViewEvent.LOGOUT));
  20:         }
  21:         
  22:         /**
  23:          * Enable or disable the connect button depending on whether or not the user has entered something into both username and password fields
  24:          */
  25:         private function usernamePasswordChange():void {
  26:             connectButton.enabled = (usernameTextInput.text.length > 0 && passwordTextInput.length > 0);
  27:         }
  28:         
  29:         /**
  30:          * Show an invalid login alert and clear the username and password fields
  31:          */
  32:         public function showInvalidLoginAlert():void {
  33:             // Popup an alert
  34:             Alert.show("Invalid username/password", "Error", Alert.OK, this);
  35:             
  36:             // Clear the input fields and notify the change handler (this will disable the connect button)
  37:             usernameTextInput.text = "";
  38:             passwordTextInput.text = "";
  39:             usernamePasswordChange();
  40:         }
  41:         
  42:         ]]>
  43:     </mx:Script>
  44:     
  45:     <mx:Form defaultButton="{connectButton}" paddingTop="0" paddingBottom="0" paddingLeft="0" paddingRight="0">
  46:         
  47:         <mx:HBox>
  48:             
  49:             <mx:Label text="Username:" selectable="false" fontSize="14" />
  50:             <mx:TextInput id="usernameTextInput" width="100" change="usernamePasswordChange()" />
  51:             
  52:             <mx:Label text="Password:" selectable="false" fontSize="14" />
  53:             <mx:TextInput id="passwordTextInput" change="usernamePasswordChange()" displayAsPassword="true" width="100" />
  54:             
  55:             <mx:Label text="Server:" fontSize="14" />
  56:             <mx:ComboBox id="serverComboBox" editable="true">
  57:                 <mx:ArrayCollection>
  58:                     <mx:String>jabber.se</mx:String>
  59:                     <mx:String>jabber.org</mx:String>
  60:                 </mx:ArrayCollection>
  61:             </mx:ComboBox>
  62:             
  63:             <mx:Button id="connectButton" label="Connect" enabled="false" click="onConnectClick()" />
  64:             <mx:Button id="disconnectButton" label="Disconnect" enabled="false" click="onDisconnectClick()" />
  65:             
  66:         </mx:HBox>
  67:         
  68:     </mx:Form>
  69:     
  70: </mx:Canvas>

We’ll also need to create the custom LoginViewEvent (in the events folder):

   1: package org.davekeen.xiffer.events {
   2:     import flash.events.Event;
   3:     
   4:     /**
   5:     * Events passed between the login view component and its mediator
   6:     * 
   7:     * @author Dave Keen
   8:     */
   9:     public class LoginViewEvent extends Event {
  10:         
  11:         public static const REGISTER:String = "login_view_register";
  12:         public static const LOGIN:String = "login_view_login";
  13:         public static const LOGOUT:String = "login_view_logout";
  14:         
  15:         private var username:String;
  16:         private var password:String;
  17:         private var server:String;
  18:         
  19:         public function LoginViewEvent(type:String, username:String = null, password:String = null, server:String = null, bubbles:Boolean = false, cancelable:Boolean = false) { 
  20:             super(type, bubbles, cancelable);
  21:             
  22:             this.username = username;
  23:             this.password = password;
  24:             this.server = server;
  25:         }
  26:         
  27:         public function getUsername():String {
  28:             return username;
  29:         }
  30:         
  31:         public function getPassword():String {
  32:             return password;
  33:         }
  34:         
  35:         public function getServer():String {
  36:             return server;
  37:         }
  38:         
  39:         public override function clone():Event { 
  40:             return new LoginViewEvent(type, username, password, server, bubbles, cancelable);
  41:         }
  42:         
  43:     }
  44:     
  45: }

Now we’re ready to start the interesting bit – implementing our LoginMediator.  These are the steps I take when implementing a mediator:

  1. Add listeners for all the events dispatched from the view component to the constructor and create event listener methods for them.
  2. Identify which notifications this mediator is interested in and add them to the listNotificationInterests method’s array and the handleNotification method’s switch statement.
  3. Fill in the event listener methods and switch statement clauses.

Now we’ll do each of these steps in turn for our LoginMediator.

1. Add listeners

Our view component dispatches LoginViewEvent.LOGIN and LoginViewEvent.LOGOUT event, so we’ll add our listeners in the constructor and add two empty event listener methods:

   1: public function LoginMediator(viewComponent:Object) {
   2:     // pass the viewComponent to the superclass where 
   3:     // it will be stored in the inherited viewComponent property
   4:     super(NAME, viewComponent);
   5:     
   6:     loginView.addEventListener(LoginViewEvent.LOGIN, onConnectClick);
   7:     loginView.addEventListener(LoginViewEvent.LOGOUT, onDisconnectClick);
   8: }
   9:  
  10: /**
  11:  * The connect button was clicked in the view
  12:  * 
  13:  * @param    loginViewEvent
  14:  */
  15: private function onConnectClick(loginViewEvent:LoginViewEvent):void { }
  16:  
  17: /**
  18:  * The disconnect button was clicked in the view
  19:  * 
  20:  * @param    loginViewEvent
  21:  */
  22: private function onDisconnectClick(loginViewEvent:LoginViewEvent):void { }

2. Add notifications

The login view is interest in knowing if a client is connected or not (so that it can enable/disable the ‘Connect’ & ‘Disconnect’ buttons accordingly.  It is also interested in knowing if a login attempt was invalid so that it can popup the ‘Invalid username/password’ alert.  This translates into listening for ApplicationFacade.VALID_LOGIN, ApplicationFacade.INVALID_LOGIN and ApplicationFacade.DISCONNECT.

Firstly we’ll add these to the listNotificationInterests method:

   1: override public function listNotificationInterests():Array {
   2:     return [
   3:             ApplicationFacade.VALID_LOGIN,
   4:             ApplicationFacade.INVALID_LOGIN,
   5:             ApplicationFacade.DISCONNECT
   6:             ];
   7: }

Now we’ll add empty clauses for each notification in the handleNotification method’s switch statement:

   1: override public function handleNotification(note:INotification):void {
   2:     switch (note.getName()) {
   3:         case ApplicationFacade.VALID_LOGIN:
   4:             break;
   5:         case ApplicationFacade.INVALID_LOGIN:
   6:             break;
   7:         case ApplicationFacade.DISCONNECT:
   8:             break;
   9:         default:
  10:             break;        
  11:     }
  12: }

3. Fill in the event listeners and switch clauses

Let do the switch clauses first.  Its all simple stuff – in the event of a valid login we want to enable the ‘Disconnect’ button and disable the ‘Connect’ button, in the event of a disconnect we want to enable the ‘Connect’ button and disable the ‘Disconnect’ button, and in the event of an invalid login we want to popup the ‘Invalid username/password’ alert box:

   1: override public function handleNotification(note:INotification):void {
   2:     switch (note.getName()) {
   3:         case ApplicationFacade.VALID_LOGIN:
   4:             loginView.connectButton.enabled = false;
   5:             loginView.disconnectButton.enabled = true;
   6:             break;
   7:         case ApplicationFacade.INVALID_LOGIN:
   8:             loginView.showInvalidLoginAlert();
   9:             break;
  10:         case ApplicationFacade.DISCONNECT:
  11:             loginView.connectButton.enabled = true;
  12:             loginView.disconnectButton.enabled = false;
  13:             break;
  14:         default:
  15:             break;        
  16:     }
  17: }

And now lets fill in our event listeners.  Again, these are very simple – all they do is send the appropriate notification which will then get auto-mapped to the appropriate command – in this case either LoginCommand or LogoutCommand.

   1: private function onConnectClick(loginViewEvent:LoginViewEvent):void {
   2:     sendNotification(ApplicationFacade.LOGIN, loginViewEvent);
   3: }
   4:  
   5: private function onDisconnectClick(loginViewEvent:LoginViewEvent):void {
   6:     sendNotification(ApplicationFacade.LOGOUT, loginViewEvent);
   7: }

Notice that for the parameter of the notifications I am just passing the same LoginViewEvent we received from the view component.  It could be argued that this breaks encapsulation as the commands shouldn’t really know anything about events.  However, after coding a few PureMVC projects I’ve noticed that its very common for the event you receive from the view to contain the same bits of information needed by the relevant command – in this case LoginCommand needs to know the username, password and server which is exactly the information contained in a LoginViewEvent.  Because of this I don’t really see the need to create an extra object, and when passing an event as notification parameter I just think of it as a value object instead of an event, but you are certainly justified in taking another view on this.

Now that we have the mediator calling the LoginCommand and LogoutCommand we’d better fill these in.  Commands can do various different things, but a very common pattern for commands, and what we’ll be using here, is:

  1. Retrieve the proxy we want to do something with using retrieveProxy.
  2. Call a method on that proxy, possibly with parameters ripped out of the notification parameter.

With that in mind we can very simply implement LoginCommand.as:

   1: override public function execute(note:INotification):void {
   2:     var loginViewEvent:LoginViewEvent = note.getBody() as LoginViewEvent;
   3:     var xmppProxy:XMPPProxy = facade.retrieveProxy(XMPPProxy.NAME) as XMPPProxy;
   4:     
   5:     xmppProxy.connect(loginViewEvent.getUsername(), loginViewEvent.getPassword(), loginViewEvent.getServer());
   6: }

… and LogoutCommand.as:

   1: override public function execute(note:INotification):void {
   2:     var xmppProxy:XMPPProxy = facade.retrieveProxy(XMPPProxy.NAME) as XMPPProxy;
   3:     
   4:     xmppProxy.disconnect();
   5: }

Guess what?  We have a working application!  Compile the application and play about with it – you’ll be able to log in and out of Jabber servers to your heart’s content 🙂  If you download a proper jabber client (http://www.jabber.org/clients has a big list of clients for various platforms) you’ll be able to see your user coming on and offline as you click ‘Connect’ and ‘Disconnect’.

Be proud!  All that’s left for us to do now is to create a buddy list (called the Roster in Jabber parlance) and the chat windows themselves.  If you’ve come this far maybe you’d like to have a go yourself without reading further.  If not, read on – Roster view here we come.

PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Part 6 – The Application View & Mediator

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

Congratulations on getting this far – we’re getting closer to our working Jabber client 🙂  Before we get going with our first top-level mediator we’ll talk about views in a little more detail.  In PureMVC a view consists of:

  • One or more view components.  This is the thing that the user actually sees and interacts with – in Flash it will be a Sprite or MovieClip, and in Flex it will be an MXML file (or an AS file extending a flex component).
  • A mediator.  This is the PureMVC bit of the view and ‘heralds’ the view components.  Any interaction with the rest of the application is done through the mediator.  Note that although the mediator knows about the existence of the view components, the view components don’t know about existence of the mediator!
  • Events.  Although not strictly a part of the view, I find it helpful to think of events within the same bundle.  View components communicate with their mediator via events and its common to create custom events for various interactions within the view component.  For example, when we come to the Login view we’re going to be dispatching a custom LoginViewEvent to the LoginMediator when the user clicks on the ‘connect’ button.

PureMVC makes no assumptions about the way that you structure the tree of views and mediators, apart from requiring that there is one top-level mediator.  In the words of our great leader, Cliff Hall (the creator of PureMVC):

It is up to you as a developer to determine the granularity of the View Component that is handled a given Mediator. If a Mediator becomes too bloated dealing with all the children of its View Component simply create a Mediator for the more complicated child. For instance, if the child components of the Application instance are complicated enough to justify their own Mediators, then the ApplicationMediator typically creates and registers the appropriate Mediator for each of those children.

This means that you start off with one mediator for your application entry point (i.e. Application.mxml) and then add extra mediators as needed.  In general you tend to have one mediator per visual ‘section’ of your application, but this is by no means enforced.

Create our ApplicationMediator.as in the view folder with Add->New Mediator… (if you don’t see this menu item be sure you’ve installed the PureMVC FlashDevelop templates from PureMVC: First thoughts & FlashDevelop templates correctly).

At this point its a good idea to add in a helper method to allow you to retrieve the view component that this mediator is looking after (in this case Application.mxml).  To do this add the following private getter:

   1: private function get application():Application {
   2:     return viewComponent as Application;
   3: }

This saves having to constantly case viewComponent to the correct class every time we use it.  Unfortunately I couldn’t find a way to get a FlashDevelop template to downcase the class name so we can’t generate this function within the template, but you’ll soon get into the habit of typing it each time you create a new mediator.

Finally we need to add our new mediator to PureMVC using the registerMediator command in StartupCommand.  The execute method in this command should now read:

   1: override public function execute(notification:INotification):void {
   2:     facade.registerProxy(new XMPPProxy());
   3:     
   4:     facade.registerMediator(new ApplicationMediator(notification.getBody() as Application));
   5: }

Notice the argument passed to the Mediator – this is the view component that the mediator is supposed to look after (in this case Application.mxml).  notification.getBody() retrieves the argument passed along with the notification, and since we sent the notification (in Application.mxml) using facade.sendNotification(ApplicationFacade.STARTUP, this) that argument will be the Application object itself!

Now we’ll create the Login view and mediator.

PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Part 5 – Model & Proxy

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

The model is the ‘data’ of our application and the proxy is our interface onto that data.  For our particular application the model itself is basically our Jabber connection object, so the Proxy will encapsulate that and expose an interface with the following methods:

  • connect(username:String, password:String, server:String):void
  • disconnect():void
  • sendMessage(message:Message):void
  • getRosterDataProvider():ArrayCollection

As you can see, the interface is very similar to our use case and commands, and this in no coincidence; each command is going to call the relevant method in its execute method.

Create a Proxy in the model folder called XMPPProxy.as using Add->New Proxy… (if you don’t see this menu item be sure you’ve installed the PureMVC FlashDevelop templates from PureMVC: First thoughts & FlashDevelop templates correctly).

I’m just going to include the Proxy code here without much explanation as it doesn’t really do anything overly complicated (all of the hard stuff has been done for us in the XIFF library 🙂 )  Have a read through the comments of each method and everything should be clear.

   1: /*
   2: Proxy - PureMVC
   3: */
   4: package org.davekeen.xiffer.model {
   5:     import flash.events.Event;
   6:     import flash.system.Security;
   7:     import org.davekeen.xiffer.ApplicationFacade;
   8:     import org.jivesoftware.xiff.core.JID;
   9:     import org.jivesoftware.xiff.core.XMPPSocketConnection;
  10:     import org.jivesoftware.xiff.data.Message;
  11:     import org.jivesoftware.xiff.data.Presence;
  12:     import org.jivesoftware.xiff.events.*
  13:     import org.jivesoftware.xiff.im.Roster;
  14:     import org.puremvc.as3.interfaces.IProxy;
  15:     import org.puremvc.as3.patterns.proxy.Proxy;
  16:     import mx.collections.ArrayCollection;
  17:  
  18:     /**
  19:      * Proxy to XMPP server
  20:      */
  21:     public class XMPPProxy extends Proxy implements IProxy {
  22:         
  23:         public static const NAME:String = "XMPPProxy";
  24:         
  25:         private var xmppSocketConnection:XMPPSocketConnection;
  26:         private var roster:Roster;
  27:  
  28:         public function XMPPProxy(data:Object = null) {
  29:             super(NAME, data);
  30:             
  31:             setupConnection();
  32:             configureListeners();
  33:         }
  34:         
  35:         /**
  36:          * Create the required XMPP objects and do any configuration on them that we might require
  37:          */
  38:         private function setupConnection():void {
  39:             xmppSocketConnection = new XMPPSocketConnection();
  40:             
  41:             roster = new Roster();
  42:             roster.connection = xmppSocketConnection;
  43:         }
  44:         
  45:         private function configureListeners():void {
  46:             // Add event listeners related to the connection
  47:             xmppSocketConnection.addEventListener(LoginEvent.LOGIN, onLogin);
  48:             xmppSocketConnection.addEventListener(XIFFErrorEvent.XIFF_ERROR, onXiffError);
  49:             xmppSocketConnection.addEventListener(DisconnectionEvent.DISCONNECT, onDisconnect);
  50:             
  51:             // Add event listeners related to messages
  52:             xmppSocketConnection.addEventListener(MessageEvent.MESSAGE, onMessage);
  53:             
  54:         }
  55:         
  56:         /**
  57:          * Attempt to connect to a XMPP server
  58:          * 
  59:          * @param    username
  60:          * @param    password
  61:          * @param    server
  62:          */
  63:         public function connect(username:String, password:String, server:String):void {
  64:             // Attempt to load a crossdomain permissions file
  65:             Security.loadPolicyFile(server + "/crossdomain.xml");
  66:             
  67:             // Connect using standard profile
  68:             xmppSocketConnection.username = username;
  69:             xmppSocketConnection.password = password;
  70:             xmppSocketConnection.server = server;
  71:             xmppSocketConnection.connect("standard");
  72:         }
  73:         
  74:         /**
  75:          * Disconnect from a XMPP server.  If not currently connected this will have no effect.
  76:          * 
  77:          */
  78:         public function disconnect():void {
  79:             xmppSocketConnection.disconnect();
  80:         }
  81:         
  82:         /**
  83:          * Return the roster as a data provider
  84:          * 
  85:          * @return
  86:          */
  87:         public function getRosterDataProvider():ArrayCollection {
  88:             return roster;
  89:         }
  90:         
  91:         /**
  92:          * Send a message to the server
  93:          * 
  94:          * @param    message
  95:          */
  96:         public function sendMessage(message:Message):void {
  97:             xmppSocketConnection.send(message);
  98:         }
  99:         
 100:         /**
 101:          * The user has successfully logged on to the XMPP server
 102:          * 
 103:          * @param    connectionSuccessEvent
 104:          */
 105:         private function onLogin(loginEvent:LoginEvent):void {
 106:             roster.setPresence(Presence.SHOW_CHAT, "", 0);
 107:             
 108:             sendNotification(ApplicationFacade.VALID_LOGIN);
 109:         }
 110:         
 111:         /**
 112:          * There has been a Jabber error - most likely an incorrect username/password error
 113:          * 
 114:          * @param    xiffErrorEvent
 115:          */
 116:         private function onXiffError(xiffErrorEvent:XIFFErrorEvent):void {
 117:             if (xiffErrorEvent.errorCode == 400)
 118:                 sendNotification(ApplicationFacade.INVALID_LOGIN);
 119:             
 120:         }
 121:         
 122:         /**
 123:          * The user has disconnected from the XMPP server
 124:          * 
 125:          * @param    disconnectionEvent
 126:          */
 127:         private function onDisconnect(disconnectionEvent:DisconnectionEvent):void {
 128:             sendNotification(ApplicationFacade.DISCONNECT);
 129:         }
 130:         
 131:         /**
 132:          * Received a message from the server
 133:          * 
 134:          * @param    messageEvent
 135:          */
 136:         private function onMessage(messageEvent:MessageEvent):void {
 137:             sendNotification(ApplicationFacade.RECEIVE_MESSAGE, messageEvent.data);
 138:         }
 139:         
 140:     }
 141: }

One thing you will notice is that the proxy dispatches another few notifications that we haven’t included in our ApplicationFacade:

  • VALID_LOGIN
  • INVALID_LOGIN
  • RECEIVE_MESSAGE
  • DISCONNECT

So lets go back to our ApplicationFacade and add them in:

   1: public static const VALID_LOGIN:String = "valid_login";
   2: public static const INVALID_LOGIN:String = "invalid_login";
   3: public static const DISCONNECT:String = "disconnect";
   4: public static const RECEIVE_MESSAGE:String = "receive_message";

The final thing we need to do is register our new Proxy with PureMVC.  We do this in StartupCommand.as using the registerProxy method:

   1: override public function execute(notification:INotification):void {
   2:     facade.registerProxy(new XMPPProxy());
   3: }

Its quite easy to forget to do this and end up with all kinds of strange errors, so be sure to remember to register any proxies you create.

We’ve finally got the bones of our application up and running so now its on to the views and mediators!

PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Part 4 – Notifications, Commands & Use Cases

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

Notifications are the nuts and bolts of a PureMVC application and are used to communicate between the various actors of your application. Notifications can be used for the following paths of communication:

  • Mediator -> Mediator
  • Mediator -> Command
  • Command -> Command
  • Command -> Mediator
  • Proxy -> Mediator
  • Proxy -> Command

In other words, Commands and Mediators listen out for notifications, and everything can send them. The ‘pattern’ reason for Proxies not being able to directly listen for notifications is to try and encourage the developer to use a command to do this. In other words, if a mediator wanted to effect a change on a proxy it might send a DO_SOMETHING notification, which would invoke DoSomethingCommand which would then retrieve the SomethingProxy and call doSomething() on it. This is less complicated than it sounds and there will be examples of this in the code we’ll be writing.

PureMVC also makes it possible for a mediator to directly retrieve a proxy and call methods on it that change its state, although this is often frowned upon by MVC purists. Having said that, there are some situations when it makes more sense to do this in simple cases rather than run through the Mediator->Command->Proxy chain (probably creating an extra command along the way). Always remember that MVC guidelines are just that – guidelines 🙂

Use case diagram

Use cases

Here’s the use case diagram for our user. Its useful to map these out at the start of the project as there is often a 1-1 mapping between use cases and commands. So now lets create these commands and map them to some notifications (we’ll leave them empty for the moment, but fill them in later).

To add an empty command right-click on the controller folder in the project area and select Add->New SimpleCommand… (if you don’t see this menu item be sure you’ve installed the PureMVC FlashDevelop templates from PureMVC: First thoughts & FlashDevelop templates correctly). Add these three commands:

  • LoginCommand.as
  • LogoutCommand.as
  • SendMessageCommand.as

Now we need to setup our notification. Notification names are just strings, so we need to setup static constants for each one. For larger projects with a lot of notifications its usual to create extra classes to hold the constants, but since we are only going to have a few of them we’ll put them in ApplicationFacade.as.

   1: public static const LOGIN:String = "login";
   2: public static const LOGOUT:String = "logout";
   3: public static const SEND_MESSAGE:String = "send_message";

Now we need to map these notifications to their associated commands. This means that whenever one of these notifications is sent PureMVC will automatically invoke its mapped command. To do this we call the registerCommand method in the initializeController method of ApplicationFacade (note that the STARTUP->StartupCommand notification was already setup in the FlashDevelop ApplicationFacade template).

   1: // Register commands with the controller
   2: override protected function initializeController():void {
   3:     super.initializeController();
   4:
   5:     registerCommand(STARTUP, StartupCommand);
   6:
   7:     registerCommand(LOGIN, LoginCommand);
   8:     registerCommand(LOGOUT, LogoutCommand);
   9:
  10:     registerCommand(SEND_MESSAGE, SendMessageCommand);
  11: }

Now let’s create our XMPP proxy…

PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Part 3 – Application and ApplicationFacade

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

Every application needs an entry point. PureMVC projects can in fact be thought of as having two entry points – one is the AVM entry point; the first class that is actually executed (this is the ‘real’ entry point). The other is the ApplicationFacade which kicks off the PureMVC framework and this is the class that should be considered the centre of our application.

FlashDevelop will probably have automatically created an entry point called Main.mxml – go ahead and delete this at this point as we will be replacing it with our own file.

Our ‘Flex’ entry point will be called Application.mxml (my PureMVC project entry points are always named Application.mxml or Application.as – I’m not sure if this is an official PureMVC naming convention but its always a good idea to decide on a naming scheme and them stick to it). Navigate to the org.davekeen.xiffer directory in the project area of FlashDevelop, right click and select Add->New MXML File… and in the prompt box name the new file Application.mxml and click OK.

Here’s the code for our application entry point:

   1: <?xml version="1.0" encoding="utf-8"?>

   2: <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"

   3:     xmlns:view="org.davekeen.xiffer.view.components.*"

   4:     layout="absolute"

   5:     width="760" height="440"

   6:     verticalGap="0"

   7:     horizontalGap="0"

   8:     creationComplete="facade.sendNotification(ApplicationFacade.STARTUP, this);">

   9:     <mx:Script>

  10:         <![CDATA[

  11:         import org.davekeen.xiffer.ApplicationFacade;

  12:

  13:         private var facade:ApplicationFacade = ApplicationFacade.getInstance();

  14:         ]]>

  15:     </mx:Script>

  16:

  17: </mx:Application>

This MXML file has no function at all apart from sending a STARTUP notification, which will kick off our PureMVC application. Later we’ll add the top-level view components to this, but for now we’re just interested in getting the basic framework up and running. In order to let FlashDevelop know that this is the entry point right-click the file in the project area and select Always Compile from the popup menu.

Now we need the ApplicationFacade. Right click on the xiffer folder in the project area and select Add->New ApplicationFacade… and name it ApplicationFacade.as. If you can’t see New ApplicationFacade… in the Add menu be sure you have installed the PureMVC FlashDevelop templates from PureMVC: First thoughts & FlashDevelop templates correctly.

Finally we need a StartupCommand. Right click on the controller folder and select Add->New SimpleCommand… and name it StartupCommand.as. Let go for a classic – in the execute method add:

trace(“Hello world!”);

Your StartupCommand.as should now look like this:

   1: /*

   2: Simple Command - PureMVC

   3:  */

   4: package org.davekeen.xiffer.controller {

   5:     import org.puremvc.as3.interfaces.INotification;

   6:     import org.puremvc.as3.patterns.command.SimpleCommand;

   7:     import org.puremvc.as3.patterns.observer.Notification;

   8:

   9:     /**

  10:      * SimpleCommand

  11:      */

  12:     public class StartupCommand extends SimpleCommand {

  13:

  14:         override public function execute(note:INotification):void {

  15:             trace("Hello world!");

  16:         }

  17:

  18:     }

  19: }

And there we have a working Flex/PureMVC HelloWorld application! Run it and feel proud 🙂

Now lets add some notifications…

PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Part 2 – Directory structure

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

We need to create a PureMVC-friendly folder structure for our application – right click on src and create org, then within that create davekeen, then within that create xiffer.  This will be the base package for our Jabber client.  Now we need folders for the various bits of our application.  Within xiffer create three folders named controller, view, model and events.  Finally within view create a folder called components.  We should have ended up with a folder structure that looks like this:

org
davekeen
—–xiffer
——-controller
——-events
——-model
——-view
———components

Now is a good time to explain what each folder’s contents and functions are.  If you haven’t already done so you should have a read through the PureMVC best practices and framework overview as it will make things a lot clearer.

org.davekeen.xiffer

This is the base package of our application and will contain Application.mxml (the Flex entry point) and ApplicationFacade.as (the PureMVC entry point).  The rest of the application will be contained in the other folders.

org.davekeen.xiffer.controller

The controller package contains commands which implement individual pieces of business logic.  For our Jabber client this will be things like login, logout and send message.

org.davekeen.xiffer.model

The model package contains proxies which are the bits of code that do all the dirty work.  All communication between our application and the Jabber server will happen within the proxy; in fact this is the only bit of the application that will even know that a Jabber server exists.

org.davekeen.xiffer.view.components

The components packages contains our actual MXML files – the things we’ll see on the screen.  Cliff Hall has put a lot of thought into the design of PureMVC and these components know nothing about the framework or internals of our app.  When things happen they dispatch events, and they might expose public methods which the framework can invoke.

org.davekeen.xiffer.view

The view package contains mediators which control our components.  In some MVC frameworks this folder might contain the actual objects that are displayed (i.e. subclassing DisplayObject), but PureMVC adds an extra level of abstraction.  The mediators know about PureMVC, but the components are completely self-contained and rely on their associated mediators to do any application-wide communication.

org.davekeen.xiffer.events

The majority of communication within PureMVC is done using notifications, but the only exception to this is communication from components to their mediators which is done using normal AS3 events.  Its also perfectly acceptable to put this package within the view folder.

Onto part 3…

PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Part 1 – Frameworks

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

Now that we’ve got a basic FlashDevelop project setup we can install the frameworks we’ll be using.

PureMVC

Download the PureMVC framework from here. Put this into a directory somewhere on your machine and add this to the FlashDevelop project classpath like so:

  1. Right click on ‘XIFFer’ and select Properties…
  2. Go to the Classpaths tab
  3. Click Add Classpath… and in the directory selector choose the PureMVC src folder.

XIFF

XIFF is an excellent Actionscript XMPP (Jabber) framework that we’ll be using to take care of the internals of Jabber communication. Its been around since Actionscript 2 but has recently been ported to Actionscript 3 (albeit in beta form). Download it here, put it into a directory and add the classpath as above.

As XIFF is currently in beta you’ll need to make a small change in order to get it to play nice with ejabberd – a common Jabber server written in Erlang. Research tells me that this is actually a problem with ejabberd’s implementation rather than XIFF’s, but whatever the issue might be this will fix it 🙂

  1. Open org.jivesoftware.xiff.core.XMPPSocketConnection
  2. Goto line 108
  3. Remove the version=”1.0″ / so that the line now reads:

openingStreamTag = “<?xml version=”1.0″?><stream:stream to=”” + server + “” xmlns=”jabber:client” xmlns:stream=”http://etherx.jabber.org/streams”>”;

Now we’re all sorted with the bits we require and its time to set up our directories and packages.

PureMVC Tutorial – Flex, PureMVC, Jabber and XIFF 3: Introduction

Introduction
Part 1 – Frameworks
Part 2 – Directory structure
Part 3 – Application and ApplicationFacade
Part 4 – Notifications, Commands & Use Cases
Part 5 – Model & Proxy
Part 6 – The Application View & Mediator
Part 7 – The Login View & Mediator
Part 8 – The Roster View & Mediator
Part 9 – The Chat View & Mediator
Conclusion, Demo & Downloads

I like Actionscript 3, I like Flex, I like Flash and I especially like PureMVC. In fact, I like them so much that its about time I wrote a fully fledged tutorial to help the rest of you like them as much as I do. The code we are going to recreate here started life as a technical test for a job I was interested in. Unfortunately it ended up not being for me, but the code itself lends itself excellently to demonstrating how to use PureMVC as well as creating a decent application along the way. As you have probably guessed from the title we’ll be creating a simple but fully functional Jabber chat client. Its not exactly going to be feature rich, but by the end of this tutorial your application will allow you to login, logout, show your buddy list and have one-to-one chats with your friends. Chatrooms, invites and all the other bits of Jabber goodness are left as an exercise for the reader 🙂

Before we start I should also humbly point out that there are many ways to program using PureMVC – what I’ve presented in this tutorial is the way that I like to do it, and the way that makes the most sense to me. However there are many equally valid ways to develop within a framework and you shouldn’t take my word as gospel, but work in whichever way you find suits you best.

Note that I’ve programmed the client using Flex merely because its quicker to create popup windows, form elements, etc in Flex than Flash. However, the bones of the app are valid in both so even if you don’t use Flex often you should still be able to get something out of this.

Before we get going, you’ll need the following:

Now we have the tools, its time to setup our project. We’re going to create an empty FlashDevelop project ready to receive our code. Open FlashDevelop and select Project->New Project. Choose Flex 3 project from the list, name the project ‘XIFFer’, check ‘Create directory for project’ and finally click OK to create the new project.

Finally we need to set the dimensions of our Flex application

  1. Right click on ‘XIFFer’ and select Properties…
  2. Set the dimensions to 760 x 400 px
  3. Click OK

We’ve got everything we need to get going! Continue onto part 1…