MACROMEDIA FLASH 8-FLASH LITE 2.X ACTIONSCRIPT LANGUAGE - Page 568

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
See also
addProperty (Object.addProperty method), unwatch (Object.unwatch method)