/hippo/src/main/webapp/ext/src/util/core/DelayedTask.js

 1/*!
 2 * Ext JS Library 3.0.0
 3 * Copyright(c) 2006-2009 Ext JS, LLC
 4 * licensing@extjs.com
 5 * http://www.extjs.com/license
 6 */
 7/**
 8 * @class Ext.util.DelayedTask
 9 * <p> The DelayedTask class provides a convenient way to "buffer" the execution of a method,
10 * performing setTimeout where a new timeout cancels the old timeout. When called, the
11 * task will wait the specified time period before executing. If durng that time period,
12 * the task is called again, the original call will be cancelled. This continues so that
13 * the function is only called a single time for each iteration.</p>
14 * <p>This method is especially useful for things like detecting whether a user has finished
15 * typing in a text field. An example would be performing validation on a keypress. You can
16 * use this class to buffer the keypress events for a certain number of milliseconds, and
17 * perform only if they stop for that amount of time.  Usage:</p><pre><code>
18var task = new Ext.util.DelayedTask(function(){
19    alert(Ext.getDom('myInputField').value.length);
20});
21// Wait 500ms before calling our function. If the user presses another key 
22// during that 500ms, it will be cancelled and we'll wait another 500ms.
23Ext.get('myInputField').on('keypress', function(){
24    task.{@link #delay}(500); 
25});
26 * </code></pre> 
27 * <p>Note that we are using a DelayedTask here to illustrate a point. The configuration
28 * option <tt>buffer</tt> for {@link Ext.util.Observable#addListener addListener/on} will
29 * also setup a delayed task for you to buffer events.</p> 
30 * @constructor The parameters to this constructor serve as defaults and are not required.
31 * @param {Function} fn (optional) The default function to timeout
32 * @param {Object} scope (optional) The default scope of that timeout
33 * @param {Array} args (optional) The default Array of arguments
34 */
35Ext.util.DelayedTask = function(fn, scope, args){
36    var me = this,
37    	id,    	
38    	call = function(){
39    		clearInterval(id);
40	        id = null;
41	        fn.apply(scope, args || []);
42	    };
43	    
44    /**
45     * Cancels any pending timeout and queues a new one
46     * @param {Number} delay The milliseconds to delay
47     * @param {Function} newFn (optional) Overrides function passed to constructor
48     * @param {Object} newScope (optional) Overrides scope passed to constructor
49     * @param {Array} newArgs (optional) Overrides args passed to constructor
50     */
51    me.delay = function(delay, newFn, newScope, newArgs){
52        me.cancel();
53        fn = newFn || fn;
54        scope = newScope || scope;
55        args = newArgs || args;
56        id = setInterval(call, delay);
57    };
58
59    /**
60     * Cancel the last queued timeout
61     */
62    me.cancel = function(){
63        if(id){
64            clearInterval(id);
65            id = null;
66        }
67    };
68};