Macromedia flex 2 Manuale

52

Using Metadata Tags in Custom Components

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Before a public, protected, or private property defined as a variable to make that specific 
property support binding. 

The tag can have the following forms:

[Bindable]
public var foo;

The Flex compiler automatically generates an event named 

propertyChange

 for the 

property. If the property value remains the same on a write, Flex does not dispatch the 
event or update the property. 

You can also specify the event name, as the following example shows:

[Bindable(event="fooChanged")]
public var foo;

In this case, you are responsible for generating and dispatching the event, typically as part 
of some other method of your class. You can specify a 

[Bindable]

 tag that includes the 

event

 specification if you want to name the event, even when you already specified the 

[Bindable]

 tag at the class level. 

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Before a public, protected, or private property defined by a getter or setter method.

You must define both a setter and a getter method to use the 

[Bindable]

 tag with the 

property. If you define just a setter method, you create a write-only property that you 
cannot use as the source of a data-binding expression. If you define just a getter method, 
you create a read-only property that you can use as the source of a data-binding expression 
without inserting the 

[Bindable] 

metadata tag. This is similar to the way that you can 

use a variable, defined by using the 

const

 keyword, as the source for a data binding 

expression. 

The tag can have the following forms:

[Bindable]
public function set shortNames(val:Boolean):void {

...

}

public function get shortNames():Boolean {

...

}

The Flex compiler automatically generates an event named 

propertyChange

 for the 

property. If the property value remains the same on a write, Flex does not dispatch the 
event or update the property. To determine if the property value changes, Flex calls the 
getter method to obtain the current value of the property.