Flex Bindings in AS3 Projects

Since 99.9% of the work we do is Flash, we pretty much use flex builder to develop Actionscript Projects. One of the things I really wanted to have was bindings. Here's how to use Flex Bindings in Actionscript only projects.

Remember that the Flash framework (textfields, movieclips, sprites, etc) doesn't dispatch the data-binding event. This means that pretty much the only things you can bind are variables.

Make sure you add the flex framework.swc to your project Library Path to have access to the mx.binding.util class.

ChangeWatcher:

Acts like the watch on AS2. It watches a variable for changes and when something happens fires an event. Make sure you call the canWatch to ensure that you can watch it!

There are 3 ways to specify the second parameter, the chain.

1. A String containing the name of a public bindable property of the host object.

   ChangeWatcher.watch(this, "myvar", handler)

2. An Object in the form: { name: property name, access: function(host) { return host[name] } }. The Object contains the name of a public bindable property, and a function which serves as a getter for that property.

   ChangeWatcher.watch(this, { name:"myvar", getter: function():String { return "something" }}, handler);

3. 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 host.a.b.c, call the method as: watch(host, ["a","b","c"]

BindingUtils.bindProperty

Works pretty much the same way as the watch, but instead of having to handle and event it allows you to immediately bind two properties one-way.
The first two parameters are for the the target, the second parameters are the triggers.

BindingUtils.bindProperty( this, "va1", this, "var2");

you can also use the same syntax for the chain.

References: