| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><!-- saved from url=(0014)about:internet --><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><link rel="stylesheet" href="../../../style.css" type="text/css" media="screen"><link rel="stylesheet" href="../../../print.css" type="text/css" media="print"><link rel="stylesheet" href="../../../override.css" type="text/css"><meta name="keywords" content="ChangeWatcher,mx.binding.utils.ChangeWatcher,useWeakReference,bindProperty,bindSetter,canWatch,getEvents,getValue,isWatching,reset,setHandler,unwatch,watch"><title>mx.binding.utils.ChangeWatcher</title></head><body><script language="javascript" type="text/javascript" src="../../../asdoc.js"></script><script language="javascript" type="text/javascript" src="../../../help.js"></script><script language="javascript" type="text/javascript" src="../../../cookies.js"></script><script language="javascript" type="text/javascript"><!-- |
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| </script><table class="titleTable" cellpadding="0" cellspacing="0" id="titleTable" style="display:none"><tr><td class="titleTableTitle" align="left">Apache Flex 4.16.1 API Reference </td><td class="titleTableTopNav" align="right"><a href="../../../package-summary.html" onclick="loadClassListFrame('../../../all-classes.html')">All Packages</a> | <a href="../../../class-summary.html" onclick="loadClassListFrame('../../../all-classes.html')">All Classes</a> | <a href="../../../all-index-A.html" onclick="loadClassListFrame('../../../index-list.html')">Index</a> | <a id="framesLink1" href="../../../index.html?mx/binding/utils/ChangeWatcher.html&mx/binding/utils/class-list.html">Frames</a><a id="noFramesLink1" style="display:none" href="" onclick="parent.location=document.location"> No Frames </a></td><td class="titleTableLogo" align="right" rowspan="3"><img src="../../../images/logo.jpg" class="logoImage" alt="AdobeLogo" title="AdobeLogo"></td></tr><tr class="titleTableRow2"><td class="titleTableSubTitle" id="subTitle" align="left">ChangeWatcher</td><td class="titleTableSubNav" id="subNav" align="right"><a href="#propertySummary">Properties</a> | <a href="#methodSummary">Methods</a></td></tr><tr class="titleTableRow3"><td colspan="3"> </td></tr></table><script language="javascript" type="text/javascript" xml:space="preserve"> |
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| </script><div xmlns:fn="http://www.w3.org/2005/xpath-functions" class="MainContent"><table class="classHeaderTable" cellpadding="0" cellspacing="0"><tr><td class="classHeaderTableLabel">Package</td><td><a href="package-detail.html" onclick="javascript:loadClassListFrame('class-list.html')">mx.binding.utils</a></td></tr><tr><td class="classHeaderTableLabel">Class</td><td class="classSignature">public class ChangeWatcher</td></tr><tr><td class="classHeaderTableLabel">Inheritance</td><td class="inheritanceList">ChangeWatcher <img src="../../../images/inherit-arrow.gif" title="Inheritance" alt="Inheritance" class="inheritArrow"> Object</td></tr></table><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p></p><p></p> |
| The ChangeWatcher class defines utility methods |
| that you can use with bindable Flex properties. |
| These methods let you define an event handler that is executed |
| whenever a bindable property is updated. |
| |
| <p></p><br/><hr></div><a name="propertySummary"></a><div class="summarySection"><div class="summaryTableTitle">Public Properties</div><table cellspacing="0" cellpadding="3" class="summaryTable " id="summaryTableProperty"><tr><th> </th><th colspan="2">Property</th><th class="summaryTableOwnerCol">Defined By</th></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><a href="#useWeakReference" class="signatureLink">useWeakReference</a> : Boolean<div class="summaryTableDescription"> |
| Determines whether the reference to handler |
| is strong or weak.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr></table></div><a name="methodSummary"></a><div class="summarySection"><div class="summaryTableTitle">Public Methods </div><table cellspacing="0" cellpadding="3" class="summaryTable " id="summaryTableMethod"><tr><th> </th><th colspan="2">Method</th><th class="summaryTableOwnerCol">Defined By</th></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><div class="summarySignature"><a href="#ChangeWatcher()" class="signatureLink">ChangeWatcher</a>(access:Object, handler:Function, commitOnly:Boolean = false, next:<a href="../../../mx/binding/utils/ChangeWatcher.html">ChangeWatcher</a> = null)</div><div class="summaryTableDescription"> |
| Constructor.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><div class="summarySignature"><a href="#canWatch()" class="signatureLink">canWatch</a>(host:Object, name:String, commitOnly:Boolean = false):Boolean</div><div class="summaryTableDescription">[static] |
| Lets you determine if the host exposes a data-binding event |
| on the property.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><div class="summarySignature"><a href="#getEvents()" class="signatureLink">getEvents</a>(host:Object, name:String, commitOnly:Boolean = false):Object</div><div class="summaryTableDescription">[static] |
| Returns all binding events for a bindable property in the host object.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><div class="summarySignature"><a href="#getValue()" class="signatureLink">getValue</a>():Object</div><div class="summaryTableDescription"> |
| Retrieves the current value of the watched property or property chain, |
| or null if the host object is null.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><div class="summarySignature"><a href="#isWatching()" class="signatureLink">isWatching</a>():Boolean</div><div class="summaryTableDescription"> |
| Returns true if each watcher in the chain is attached |
| to at least one change event.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><div class="summarySignature"><a href="#reset()" class="signatureLink">reset</a>(newHost:Object):void</div><div class="summaryTableDescription"> |
| Resets this ChangeWatcher instance to use a new host object.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><div class="summarySignature"><a href="#setHandler()" class="signatureLink">setHandler</a>(handler:Function):void</div><div class="summaryTableDescription"> |
| Sets the handler function.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><div class="summarySignature"><a href="#unwatch()" class="signatureLink">unwatch</a>():void</div><div class="summaryTableDescription"> |
| Detaches this ChangeWatcher instance, and its handler function, |
| from the current host.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr><tr class=""><td class="summaryTablePaddingCol"> </td><td class="summaryTableInheritanceCol"> </td><td class="summaryTableSignatureCol"><div class="summarySignature"><a href="#watch()" class="signatureLink">watch</a>(host:Object, chain:Object, handler:Function, commitOnly:Boolean = false, useWeakReference:Boolean = false):<a href="../../../mx/binding/utils/ChangeWatcher.html">ChangeWatcher</a></div><div class="summaryTableDescription">[static] |
| Creates and starts a ChangeWatcher instance.</div></td><td class="summaryTableOwnerCol">ChangeWatcher</td></tr></table></div><script language="javascript" type="text/javascript"><!-- |
| showHideInherited(); |
| --></script><div class="MainContent"><div class="detailSectionHeader">Property Detail</div><a name="propertyDetail"></a><a name="useWeakReference"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">useWeakReference</td><td class="detailHeaderType">property</td></tr></table><div class="detailBody"><code>public var useWeakReference:Boolean</code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p> |
| Determines whether the reference to <code>handler</code> |
| is strong or weak. |
| A strong reference (the default) prevents |
| <code>handler</code> from being garbage-collected. |
| A weak reference does not. |
| </p><p> The default value is <code>false</code>.</p></div><a name="constructorDetail"></a><div class="detailSectionHeader">Constructor Detail</div><a name="ChangeWatcher()"></a><a name="ChangeWatcher(Object,Function,Boolean,mx.binding.utils.ChangeWatcher)"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">ChangeWatcher</td><td class="detailHeaderParens">()</td><td class="detailHeaderType">Constructor</td></tr></table><div class="detailBody"><code>public function ChangeWatcher(access:Object, handler:Function, commitOnly:Boolean = false, next:<a href="../../../mx/binding/utils/ChangeWatcher.html">ChangeWatcher</a> = null)</code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p> |
| Constructor. |
| Not for public use. This method is called only from the <code>watch()</code> method. |
| See the <code>watch()</code> method for parameter usage. |
| |
| </p><span class="label"> Parameters </span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20px"></td><td><code><span class="label">access</span>:Object</code></td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">handler</span>:Function</code></td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">commitOnly</span>:Boolean</code> (default = <code>false</code>)<code></code></td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">next</span>:<a href="../../../mx/binding/utils/ChangeWatcher.html">ChangeWatcher</a></code> (default = <code>null</code>)<code></code></td></tr></table></div><a name="methodDetail"></a><div class="detailSectionHeader">Method Detail</div><a name="canWatch()"></a><a name="canWatch(Object,String,Boolean)"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">canWatch</td><td class="detailHeaderParens">()</td><td class="detailHeaderType">method</td></tr></table><div class="detailBody"><code> public static function canWatch(host:Object, name:String, commitOnly:Boolean = false):Boolean</code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p> |
| Lets you determine if the host exposes a data-binding event |
| on the property. |
| |
| <p>NOTE: Property chains are not supported by the <code>canWatch()</code> method. |
| They are supported by the <code>watch()</code> method.</p> |
| </p><p><span class="label"> Parameters </span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20px"></td><td><code><span class="label">host</span>:Object</code> — The host of the property. |
| See the <code>watch()</code> method for more information. |
| </td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">name</span>:String</code> — The name of the property. |
| See the <code>watch()</code> method for more information. |
| </td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">commitOnly</span>:Boolean</code> (default = <code>false</code>)<code></code> — Set to <code>true</code> if the handler |
| should be called only on committing change events. |
| See the <code>watch()</code> method for more information. |
| </td></tr></table></p><p></p><span class="label">Returns</span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20"></td><td><code>Boolean</code> — <code>true</code> if <code>host</code> exposes |
| any change events on <code>name</code>. |
| |
| </td></tr></table></div><a name="getEvents()"></a><a name="getEvents(Object,String,Boolean)"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">getEvents</td><td class="detailHeaderParens">()</td><td class="detailHeaderType">method</td><td class="detailHeaderRule"> </td></tr></table><div class="detailBody"><code> public static function getEvents(host:Object, name:String, commitOnly:Boolean = false):Object</code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p> |
| Returns all binding events for a bindable property in the host object. |
| </p><p><span class="label"> Parameters </span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20px"></td><td><code><span class="label">host</span>:Object</code> — The host of the property. |
| See the <code>watch()</code> method for more information. |
| </td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">name</span>:String</code> — The name of the property, or property chain. |
| See the <code>watch()</code> method for more information. |
| </td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">commitOnly</span>:Boolean</code> (default = <code>false</code>)<code></code> — Controls inclusion of non-committing |
| change events in the returned value. |
| </td></tr></table></p><p></p><span class="label">Returns</span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20"></td><td><code>Object</code> — Object of the form <code>{ eventName: isCommitting, ... }</code> |
| containing all change events for the property. |
| |
| </td></tr></table></div><a name="getValue()"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">getValue</td><td class="detailHeaderParens">()</td><td class="detailHeaderType">method</td><td class="detailHeaderRule"> </td></tr></table><div class="detailBody"><code> public function getValue():Object</code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p> |
| Retrieves the current value of the watched property or property chain, |
| or null if the host object is null. |
| For example: |
| <pre> |
| watch(obj, ["a","b","c"], ...).getValue() === obj.a.b.c |
| </pre> |
| </p><p></p><span class="label">Returns</span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20"></td><td><code>Object</code> — The current value of the watched property or property chain. |
| |
| </td></tr></table></div><a name="isWatching()"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">isWatching</td><td class="detailHeaderParens">()</td><td class="detailHeaderType">method</td><td class="detailHeaderRule"> </td></tr></table><div class="detailBody"><code> public function isWatching():Boolean</code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p> |
| Returns <code>true</code> if each watcher in the chain is attached |
| to at least one change event. |
| Note that the <code>isWatching()</code> method |
| varies with host, since different hosts may expose different change |
| events for the watcher's chosen property. |
| </p><p></p><span class="label">Returns</span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20"></td><td><code>Boolean</code> — <code>true</code> if each watcher in the chain is attached |
| to at least one change event. |
| |
| </td></tr></table></div><a name="reset()"></a><a name="reset(Object)"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">reset</td><td class="detailHeaderParens">()</td><td class="detailHeaderType">method</td><td class="detailHeaderRule"> </td></tr></table><div class="detailBody"><code> public function reset(newHost:Object):void</code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p> |
| Resets this ChangeWatcher instance to use a new host object. |
| You can call this method to reuse a watcher instance |
| on a different host. |
| </p><p><span class="label"> Parameters </span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20px"></td><td><code><span class="label">newHost</span>:Object</code> — The new host of the property. |
| See the <code>watch()</code> method for more information. |
| |
| </td></tr></table></p></div><a name="setHandler()"></a><a name="setHandler(Function)"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">setHandler</td><td class="detailHeaderParens">()</td><td class="detailHeaderType">method</td><td class="detailHeaderRule"> </td></tr></table><div class="detailBody"><code> public function setHandler(handler:Function):void</code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p> |
| Sets the handler function. |
| </p><p><span class="label"> Parameters </span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20px"></td><td><code><span class="label">handler</span>:Function</code> — The handler function. This argument must not be null. |
| |
| </td></tr></table></p></div><a name="unwatch()"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">unwatch</td><td class="detailHeaderParens">()</td><td class="detailHeaderType">method</td><td class="detailHeaderRule"> </td></tr></table><div class="detailBody"><code> public function unwatch():void</code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p> |
| Detaches this ChangeWatcher instance, and its handler function, |
| from the current host. |
| You can use the <code>reset()</code> method to reattach |
| the ChangeWatcher instance, or watch the same property |
| or chain on a different host object. |
| |
| </p></div><a name="watch()"></a><a name="watch(Object,Object,Function,Boolean,Boolean)"></a><table class="detailHeader" cellpadding="0" cellspacing="0"><tr><td class="detailHeaderName">watch</td><td class="detailHeaderParens">()</td><td class="detailHeaderType">method</td><td class="detailHeaderRule"> </td></tr></table><div class="detailBody"><code> public static function watch(host:Object, chain:Object, handler:Function, commitOnly:Boolean = false, useWeakReference:Boolean = false):<a href="../../../mx/binding/utils/ChangeWatcher.html">ChangeWatcher</a></code><p></p><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Language Version : </b></td><td>ActionScript 3.0</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Product Version : </b></td><td>Flex 3</td></tr></table><table cellpadding="0" cellspacing="0" border="0"><tr><td style="white-space:nowrap" valign="top"><b> Runtime Versions : </b></td><td>Flash Player 9, AIR 1.1</td></tr></table><p></p><p></p><p> |
| Creates and starts a ChangeWatcher instance. |
| A single ChangeWatcher instance can watch one property, |
| or a property chain. |
| A property chain is a sequence of properties accessible from |
| a host object. |
| For example, the expression |
| <code>obj.a.b.c</code> contains the property chain (a, b, c). |
| </p><p><span class="label"> Parameters </span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20px"></td><td><code><span class="label">host</span>:Object</code> — The object that hosts the property or property chain |
| to be watched. |
| You can use the use the <code>reset()</code> method to change |
| the value of the <code>host</code> argument after creating |
| the ChangeWatcher instance. |
| The <code>host</code> maintains a list of <code>handlers</code> to invoke |
| when <code>prop</code> changes. |
| </td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">chain</span>:Object</code> — A value specifying the property or chain to be watched. |
| Legal values are: |
| <ul> |
| <li>A String containing the name of a public bindable property |
| of the host object.</li> |
| <li>An Object in the form: |
| <code>{ name: <i>property name</i>, getter: function(host) { return host[name] } }</code>. |
| The Object contains the name of a public bindable property, |
| and a function which serves as a getter for that property.</li> |
| <li>A non-empty Array containing any combination |
| of the first two options. |
| This represents a chain of bindable properties |
| accessible from the host. |
| For example, to watch the property <code>host.a.b.c</code>, |
| call the method as: <code>watch(host, ["a","b","c"], ...)</code>.</li> |
| </ul> |
| <p>Note: The property or properties named in the <code>chain</code> argument |
| must be public, because the <code>describeType()</code> method suppresses all information |
| about non-public properties, including the bindability metadata |
| that ChangeWatcher scans to find the change events that are exposed |
| for a given property. |
| However, the getter function supplied when using the <code>{ name, getter }</code> |
| argument form described above can be used to associate an arbitrary |
| computed value with the named (public) property.</p> |
| </td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">handler</span>:Function</code> — An event handler function called when the value of the |
| watched property (or any property in a watched chain) is modified. |
| The modification is signaled when any host object in the watcher |
| chain dispatches the event that has been specified in that host object's |
| <code>[Bindable]</code> metadata tag for the corresponding watched property. |
| The default event is named <code>propertyChange</code>. |
| <p>The event object dispatched by the bindable property is passed |
| to this handler function without modification. |
| By default, Flex dispatches an event object of type PropertyChangeEvent. |
| However, you can define your own event type when you use the |
| <code>[Bindable]</code> metadata tag to define a bindable property.</p> |
| </td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">commitOnly</span>:Boolean</code> (default = <code>false</code>)<code></code> — Set to <code>true</code> if the handler should be |
| called only on committing change events; |
| set to <code>false</code> if the handler should be called on both |
| committing and non-committing change events. |
| Note: the presence of non-committing change events for a property is |
| indicated by the <code>[NonCommittingChangeEvent(<event-name>)]</code> metadata tag. |
| Typically these tags are used to indicate fine-grained value changes, |
| such as modifications in a text field prior to confirmation. |
| </td></tr><tr><td class="paramSpacer"> </td></tr><tr><td width="20px"></td><td><code><span class="label">useWeakReference</span>:Boolean</code> (default = <code>false</code>)<code></code> — (default = false) Determines whether |
| the reference to <code>handler</code> is strong or weak. A strong |
| reference (the default) prevents <code>handler</code> from being |
| garbage-collected. A weak reference does not. |
| </td></tr></table></p><p></p><span class="label">Returns</span><table cellpadding="0" cellspacing="0" border="0"><tr><td width="20"></td><td><code><a href="../../../mx/binding/utils/ChangeWatcher.html">ChangeWatcher</a></code> — The ChangeWatcher instance, if at least one property name has |
| been specified to the <code>chain</code> argument; null otherwise. |
| Note that the returned watcher is not guaranteed to have successfully |
| discovered and attached itself to change events, since none may have |
| been exposed on the given property or chain by the host. |
| You can use the <code>isWatching()</code> method to determine the |
| watcher's state. |
| </td></tr></table><p><span class="label">See also</span></p><div class="seeAlso"><a href="../../../mx/events/PropertyChangeEvent.html" target="">mx.events.PropertyChangeEvent</a></div></div><br/><br/><hr><br/><p></p><center class="copyright"><footer>The Apache Software Foundation</footer><br/>Wed Nov 15 2017, 09:50 AM +01:00 </center></div></body></html><!--The Apache Software Foundation<br/>Wed Nov 15 2017, 09:50 AM +01:00 --> |
