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ApplicationBroadcaster

Kind of class:	public class
Package:	com.bourre.events
Inherits from:	ChannelBroadcaster
Author:	Francis Bourre, Romain Flacher
Classpath:	com.bourre.events.ApplicationBroadcaster
File last modified:	Monday, 24 November 2008, 11:36:53

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/*
 * Copyright the original author or authors.
 * 
 * Licensed under the MOZILLA PUBLIC LICENSE, Version 1.1 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.mozilla.org/MPL/MPL-1.1.html
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.bourre.events
{
    import com.bourre.plugin.PluginBroadcaster;    

    /**
     * The <code>ApplicationBroadcaster</code> class is a singleton
     * implementation of the <code>ChannelBroadcaster</code> class, 
     * used for <i>Inversion of Controls</i> purpose. More formally
     * the application broadcaster is dedicated to plugin to plugin
     * communication. When defining a plugin with a specific channel, 
     * and then listeners of this plugin, a channel instance is created
     * in the <code>ChannelExpert</code> and then this channel is used
     * in order to create the whole dispatching stuff between these 
     * plugins.
     * <p>
     * The class defines two constant channels dedicated to an IoC usage.
     * These channel represents particular behaviors of the application
     * broadcaster. Such : 
     * <ul>
     * <li><code>NO_CHANNEL</code> : That constant, when used as argument of
     * the <code>getChannelDispatcher</code> method, force the application
     * broadcaster to ignore the call. No broadcaster will be created and
     * then returned by the function.</li>
     * <li><code>SYSTEM_CHANNEL</code> : Defines the default channel of the
     * application broadcaster singleton. All objects which add themselves
     * as listener without specifying any channel are considered as system
     * listeners.</li>
     * </ul>
     * </p>
     * 
     * @author     Francis Bourre
     * @author     Romain Flacher
     * @see        ChannelBroadcaster
     * @see        com.bourre.plugin.ChannelExpert
     */
    public class ApplicationBroadcaster    extends ChannelBroadcaster
    {
        private static var _oI : ApplicationBroadcaster;

        /**
         * Inhibit the behavior of the <code>getChannelDispatcher</code>
         * which will return nothing if this channel is passed as argument.
         */
        public const NO_CHANNEL : EventChannel = new NoChannel();

        /**
         * Default channel for the application broadcaster, all listeners
         * which not define any channel are considered as system listeners.
         */
        public const SYSTEM_CHANNEL : EventChannel = new SystemChannel();

        /**
         * Returns the singleton instance of the <code>ApplicationBroadcaster</code>
         * class. The class instance is created using the lazy initialisation concept.
         * 
         * @return    singleton instance of <code>ApplicationBroadcaster</code>
         */
        public static function getInstance () : ApplicationBroadcaster 
        {
            if ( !(ApplicationBroadcaster._oI is ApplicationBroadcaster) ) 
                ApplicationBroadcaster._oI = new ApplicationBroadcaster( new PrivateConstructorAccess( ) );
                
            return ApplicationBroadcaster._oI;
        }

        /**
         * Creates a new <code>ApplicationBroadcaster</code> object. This constructor
         * is locked using a simple hack, you cannot call the constructor directly.
         * Please use the <code>ApplicationBroadcaster.getInstance</code> method instead,
         * in order to retreive the singleton instance of the class.
         * 
         * @param    access    a lock for direct instanciation of the
         *                     <code>ApplicationBroadcaster</code>    class
         */
        public function ApplicationBroadcaster ( access : PrivateConstructorAccess )
        {
            super( PluginBroadcaster, SYSTEM_CHANNEL );
        }

        /**
         * Returns the <code>EventBroadcaster</code> object associated with
         * the passed-in <code>channel<code>. The <code>owner</code> is an optionnal
         * parameter which is used to initialize the newly created <code>EventBroadcaster</code>
         * when there is no broadcaster for this channel.
         * <p>
         * There's a particular case defined by this class, when passing the <code>NO_CHANNEL</code>
         * channel in this function, the function will return <code>null</code> instead of a broadcaster.
         * </p>
         * 
         * @param    channel    the channel for which get the associated broadcaster
         * @param    owner    an optional object which will used as source if there
         *                     is no broadcaster associated to the channel
         * @return    the <code>EventBroadcaster</code> object associated with
         *             the passed-in <code>channel<code>
         */
        public override function getChannelDispatcher ( channel : EventChannel = null, owner : Object = null ) : Broadcaster
        {
            return ( channel != NO_CHANNEL ) ? super.getChannelDispatcher( channel, owner ) : null;
        }
    }
}

import com.bourre.events.EventChannel;

internal class NoChannel extends EventChannel
{
}

internal class SystemChannel extends EventChannel
{
}

internal class PrivateConstructorAccess 
{
}

The ApplicationBroadcaster class is a singleton
implementation of the ChannelBroadcaster class,
used for Inversion of Controls purpose. More formally
the application broadcaster is dedicated to plugin to plugin
communication. When defining a plugin with a specific channel,
and then listeners of this plugin, a channel instance is created
in the ChannelExpert and then this channel is used
in order to create the whole dispatching stuff between these
plugins.

The class defines two constant channels dedicated to an IoC usage.
These channel represents particular behaviors of the application
broadcaster. Such :

NO_CHANNEL : That constant, when used as argument of
the getChannelDispatcher method, force the application
broadcaster to ignore the call. No broadcaster will be created and
then returned by the function.
SYSTEM_CHANNEL : Defines the default channel of the
application broadcaster singleton. All objects which add themselves
as listener without specifying any channel are considered as system
listeners.

Summary

Constructor

ApplicationBroadcaster (access:PrivateConstructorAccess)
- Creates a new ApplicationBroadcaster object.

Constants

NO_CHANNEL : EventChannel
- Inhibit the behavior of the getChannelDispatcherwhich will return nothing if this channel is passed as argument.
SYSTEM_CHANNEL : EventChannel
- Default channel for the application broadcaster, all listeners

Class methods

getInstance : ApplicationBroadcaster
- Returns the singleton instance of the ApplicationBroadcasterclass.

Instance methods

getChannelDispatcher (channel:EventChannel = null, owner:Object = null) : Broadcaster
- Returns the EventBroadcaster object associated with

Instance methods inherited from ChannelBroadcaster

addEventListener addListener broadcastEvent empty getDefaultChannel getDefaultDispatcher hasChannelDispatcher hasChannelListener isRegistered releaseChannelDispatcher removeEventListener removeListener setDefaultChannel toString

Constructor

ApplicationBroadcaster

public function ApplicationBroadcaster (

access:PrivateConstructorAccess)

Creates a new ApplicationBroadcaster object. This constructor
is locked using a simple hack, you cannot call the constructor directly.
Please use the ApplicationBroadcaster.getInstance method instead,
in order to retreive the singleton instance of the class.

Parameters:

access:

a lock for direct instanciation of the
ApplicationBroadcaster class

Constants

NO_CHANNEL

public const NO_CHANNEL:EventChannel = new NoChannel()

(read)

Inhibit the behavior of the getChannelDispatcherwhich will return nothing if this channel is passed as argument.

SYSTEM_CHANNEL

public const SYSTEM_CHANNEL:EventChannel = new SystemChannel()

(read)

Default channel for the application broadcaster, all listeners
which not define any channel are considered as system listeners.

Class methods

getInstance

public static function getInstance (

) : ApplicationBroadcaster

Returns the singleton instance of the ApplicationBroadcasterclass. The class instance is created using the lazy initialisation concept.

Returns:

singleton instance of ApplicationBroadcaster

Instance methods

getChannelDispatcher

override public function getChannelDispatcher (

channel:EventChannel = null, owner:Object = null) : Broadcaster

Returns the EventBroadcaster object associated with
the passed-in channel<code>. The <code>owner is an optionnal
parameter which is used to initialize the newly created EventBroadcasterwhen there is no broadcaster for this channel.

There's a particular case defined by this class, when passing the NO_CHANNELchannel in this function, the function will return null instead of a broadcaster.

Parameters:

channel:

the channel for which get the associated broadcaster

owner :

an optional object which will used as source if there
is no broadcaster associated to the channel

Returns:

the EventBroadcaster object associated with
the passed-in channel

Overrides: ChannelBroadcaster.getChannelDispatcher