Creating ActionScript components

You create reusable components using ActionScript, and reference these components in your Flex applications as MXML tags. Components created in ActionScript can contain graphical elements, define custom business logic, or extend existing Flex components. They can inherit from any components available in Flex.

Defining your own components in ActionScript has several benefits. Components let you divide your applications into individual modules that you can develop and maintain separately. By implementing commonly used logic within custom components, you can build a suite of reusable components that you can share among multiple Flex applications.

In addition, you can base your custom components on the set of Flex components by extending from the Flex class hierarchy. You can create custom versions of Flex visual controls, as well as custom versions on nonvisual components, such as data validators, formatters, and effects.

For example, you can define a custom button, derived from the Flex Button control, as the following example shows:

class myControls.MyButton extends mx.controls.Button {
   function MyButton() {
      ...
   }
   ...
}

In this example, you write your MyButton control to the MyButton.as file, and you store the file in the myControls subdirectory of the root directory of your Flex application. The fully qualified class name of your component reflects its location. In this example, the component's fully qualified class name is myControls.MyButton.

You can reference your custom Button control from a Flex application file, such as MyApp.mxml, as the following example shows:

<mx:Application xmlns:mx="http://www.macromedia.com/2003/mxml" 
xmlns:cmp="myControls.*" >

   <cmp:MyButton label="Jack" />

</mx:Application>

In this example, you first define the cmp namespace that defines the location of your custom component in the application's directory structure. You then reference the component as an MXML tag using the namespace prefix.

Typically, you put custom ActionScript components in directories that are in the ActionScript classpath. These include your application's root directory, the flex_app_root/WEB-INF/flex/user_classes directory, or any directory you specify in the <actionscript-classpath> tag in the flex-config.xml file. For more information, see Creating ActionScript Components in Developing Flex Applications.

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