ComponentDescriptor  - AS3 Flex

A reference to the document Object in which the component is to be created.

Relaterade API-element

An Object containing name/value pairs for the component's event handlers, as specified in MXML.

For example, if you write

      <mx:DataGrid id="dg" initialize="fetchData(); initDataGrid();"  change="changeHandler(event);"/>
      

then the descriptor's events property is the Object

      { initialize: "__dg_initialize", change: "__dg_change" }
      

The eventproperty is null if no MXML event handlers were specified for the component

The strings "__dg_initialize" and "__dg_change" are the names of event handler methods that the MXML compiler autogenerates. The body of these methods contain the ActionScript statements that you specified as the values of the event attributes. For example, the autogenerated initialize handler is

      public function __dg_initialize(event:mx.events.FlexEvent):void
      {
          fetchData();
          initDataGrid();
      }
      

You should not assume that the autogenerated event handlers will always be specified by name; this may change in a future version of Flex.

This property is used by the Container method createComponentsFromDescriptors() to register the autogenerated event handlers using the addEventListener() method.

The identifier for the component, as specified in MXML.

For example, if you write

      <mx:TextInput id="firstName" text="Enter your first name here"/>
      

then the descriptor's id property is the String "firstName".

The id property is null if no MXML id was specified for the component.

The value of the id property becomes the name of a public variable in the MXML document object, autogenerated by the MXML compiler. The value of this variable is a reference to the UIComponent object created from this descriptor. This is why you can, for example, reference the TextInput control's text property as firstName.text from anywhere within the document containing this TextInput instance.

If an id is specified, and it isn't the empty string, it also becomes the name of the DisplayObject object. If an id is not specified or is empty, the DisplayObject object's name remains an autogenerated string, such as "Button3", as returned by the NameUtil.createUniqueName() method. The name is used in generating the string returned by the toString() method. It can also be used to find the component from its parent by calling getChildByName().

Relaterade API-element

An Object containing name/value pairs for the component's properties, as specified in MXML.

For example, if you write

      <mx:TextInput width="150" text="Hello"/>
      

then the descriptor's properties property is the Object

      { width: 150, text: "Hello" }
      

The properties property is null if no MXML properties were specified for the component. In this case, the component will use default property values.

This Object is produced by calling the function specified by the propertiesFactory property, and then cached for subsequent access. However, when a Repeater produces multiple instances of a component from the same descriptor, a fresh copy of the properties Object should be produced for each component instance so that they don't share property values which are Arrays or Object references. The Repeater accomplishes this by calling the invalidateProperties() method on the descriptor.

Relaterade API-element

A Function that returns an Object containing name/value pairs for the component's properties, as specified in MXML.

For example, if you write

      <mx:TextInput width="150" text="Hello">
      

then the descriptor's propertiesFactory property is the Function:

      function():Object { return { width: 150, text: "Hello" }; }
      

The propertiesFactoryproperty is null if no MXML properties were specified for the component. In this case, the component will use default property values.

The reason that propertyFactory is a Function returning an Object rather than an actual Object is to allow the tree of ComponentDescriptor objects to "unfold" incrementally. If all the descriptors in the descriptor tree for the document were created at launch time, the time to launch would be greater.

The properties property returns a cached Object that was produced by this factory function.

Note: Event handlers such as click="doSomething();" appear in the events Object, not in the properties Object.

Relaterade API-element

The Class of the component, as specified in MXML.

For example, if you write

      <mx:TextInput/>
      

then the descriptor's type property the Class mx.controls.TextInput.

The property is never null for the ComponentDescriptor objects created by the MXML compiler, because every MXML tag has a tag name such as mx:TextInput.

The mapping between an MXML tag and its corresponding class is determined by the XML namespace and the "manifest" file, if any, that is associated with that namespace. For example, the standard Flex namespace http://www.adobe.com/2006/mxml represented by the mx: prefix is associated (in the flex-config.xml file) with the manifest file mxml-manifest.xml, and this file has the tag

      <component id="TextInput" class="mx.controls.TextInput"/>
      

which maps the tag name mx:TextInput to the Class mx.controls.TextInput. Note that the use of a manifest file allows components in single XML namespace to map to classes in multiple ActionScript packages.

Constructor.

Invalidates the cached properties property. The next time you read the properties property, the properties are regenerated from the function specified by the value of the propertiesFactory property.

Returns the string "ComponentDescriptor_" plus the value of the id property.