User Guide

568 ActionScript classes

userData:Object [optional] - An arbitrary piece of ActionScript data that is passed to the

callback method. If the userData parameter is omitted, undefined is passed to the callback

method.

Returns

Boolean - A Boolean value: true if the watchpoint is created successfully, false otherwise.

Example

The following example uses watch() to check whether the speed property exceeds the speed

limit:

// Create a new object

var myObject:Object = new Object();

// Add a property that tracks speed

myObject.speed = 0;

// Write the callback function to be executed if the speed property changes

var speedWatcher:Function = function(prop, oldVal, newVal, speedLimit) {

// Check whether speed is above the limit

if (newVal > speedLimit) {

trace ("You are speeding.");

}

else {

trace ("You are not speeding.");

}

// Return the value of newVal.

return newVal;

}

// Use watch() to register the event handler, passing as parameters:

// - the name of the property to watch: "speed"

// - a reference to the callback function speedWatcher

// - the speedLimit of 55 as the userData parameter

myObject.watch("speed", speedWatcher, 55);

// set the speed property to 54, then to 57

myObject.speed = 54; // output: You are not speeding

myObject.speed = 57; // output: You are speeding

// unwatch the object

myObject.unwatch("speed");

myObject.speed = 54; // there should be no output