Using Objects in ActionScript > About using watchpoints to set properties

 

About using watchpoints to set properties

You can use the Object.watch method to register a callback function to be invoked when a specified property of an ActionScript object changes. When the property changes, the callback function is invoked with myObject as the containing object. You must return the new value from the object.watch callback function, or the watched object property is assigned a value of undefined.

For example, in the code that follows, the watch method specifies a function to be invoked when the value for the label property of the CheckBox component is changed:

function CheckBox() {
	...
	this.watch('label', function (id, oldval, newval){
		...
	});

}

When the label property is modified, the specified function is invoked to perform any tasks needed to update the appearance and state of the component to reflect its new parameters. Therefore, the following assignment statement uses an Object.watch handler to notify the component that the variable has changed and causes it to update its graphical representation.

myCheckBox1.value = false;

This syntax is more concise than using a method to update the label property:

myCheckBox1.setLabel(false);

To remove a watchpoint, use the Object.unwatch method.

For more information, see Object.watch and Object (object) in the ActionScript Dictionary.