gwt.dojo.core.client.MessageHub.java Source code

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Here is the source code for gwt.dojo.core.client.MessageHub.java

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/*
 * Copyright 2012 ArkaSoft LLC.
 * 
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 * 
 * 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 gwt.dojo.core.client;

import com.google.gwt.core.client.JavaScriptObject;

/**
 * A centralized hub for publishing and subscribing to global messages by topic.
 * One can subscribe to the messages by using {@code subscribe()}, and one can
 * publish by using {@link #publish(String, Object...)}.
 */
public class MessageHub extends JsObject {
    public static final String MODULE = "dojo/topic";

    /**
     * Return instance of {@code MessageHub} class.
     * 
     * @return {@code MessageHub} instance.
     */
    private static MessageHub ref() {
        return Dojo.require(MODULE);
    }

    /**
     * Not directly instantiable (required by JSNI).
     */
    protected MessageHub() {
    }

    /**
     * Publishes a message to a topic on the pub/sub hub. All arguments after
     * the first will be passed to the subscribers, so any number of arguments
     * can be provided (not just event).
     * 
     * @param topic
     *            The name of the topic to publish to.
     * @param message
     *            A message to distribute to the topic listeners.
     */
    public static void publish(String topic, Object... message) {
        JsArray args = JavaScriptObject.createArray().cast();
        if (message != null) {
            for (int i = 0, n = message.length; i < n; i++) {
                args.push(message[i]);
            }
        }
        ref()._publish(topic, args);
    };

    private final native void _publish(String topic, JsArray a) /*-{
                                                                switch (a.length) {
                                                                case 0:
                                                                this.publish(topic);
                                                                break;
                                                                case 1:
                                                                this.publish(topic, a[0]);
                                                                break;
                                                                case 2:
                                                                this.publish(topic, a[0], a[1]);
                                                                break;
                                                                case 3:
                                                                this.publish(topic, a[0], a[1], a[2]);
                                                                break;
                                                                case 4:
                                                                this.publish(topic, a[0], a[1], a[2], a[3]);
                                                                break;
                                                                case 5:
                                                                this.publish(topic, a[0], a[1], a[2], a[3], a[4]);
                                                                break;
                                                                case 6:
                                                                this.publish(topic, a[0], a[1], a[2], a[3], a[4], a[5]);
                                                                break;
                                                                case 7:
                                                                this.publish(topic, a[0], a[1], a[2], a[3], a[4], a[5], a[6]);
                                                                break;
                                                                case 8:
                                                                this.publish(topic, a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7]);
                                                                break;
                                                                default:
                                                                throw "Too many args";
                                                                }
                                                                }-*/;

    /**
     * Subscribes to a topic on the pub/sub hub.
     * 
     * @param topic
     *            The topic to subscribe to.
     * @param callback
     *            A callback to call when a message is published to the given
     *            topic.
     * @return A simple object containing a {@code remove()} method, which can
     *         be called to unsubscribe the listener.
     */
    public static SubscribeHandle subscribe(String topic, SubscribeCallback callback) {
        return ref()._subscribe(topic, callback);
    }

    private final native SubscribeHandle _subscribe(String topic, SubscribeCallback callback) /*-{
                                                                                              var func = function() {
                                                                                              try {
                                                                                              @gwt.dojo.core.client.Dojo::doCallback(Lgwt/dojo/core/client/SubscribeCallback;Ljava/lang/String;Lgwt/dojo/core/client/JsArray;)(callback, topic, arguments);
                                                                                              } catch (ex) {
                                                                                              alert("Error in subscribe callback");
                                                                                              }
                                                                                              }
                                                                                              return this.subscribe(topic, func);
                                                                                              }-*/;
}