Data binding

Syntax

MXML attributes identifying Bindable properties may contain an interpolated braces group containing an ActionScript 3 expression that is either a string literal or a member expression.

• When that braces group contains a string literal, it behaves as an escaped string that may contain braces.
• When that braces group contains a member expression, the compiler resolves that expression to a Bindable property and listens to the respective PropertyChangeEvent event, always computing the property on change.

Bindable meta-data

The [Bindable] ActionScript 3 meta-data is used to indicate that either a property or all properties of a class trigger a PropertyChangeEvent after write. The event is only dispatched if newValue !== prevValue (notice the strict !== operator).

The [Bindable] meta-data may be in one of the forms:

[Bindable]
[Bindable("eventName")]
[Bindable(event="eventName")]

If the event name is omitted, it defaults to "propertyChange".

A setter may contain the [Bindable] meta-data, behaving similiarly as above, indicating that the parent virtual slot contains a specific Bindable event name.

To support [Bindable], the bytecode generator generates event dispatch code right after the property's assignment, whether within a destructuring assignment that affects the enclosing class's instance or a direct assignment.