The Flex 3 Class Hierarchy

Understanding the Flex 3 class hierarchy is the first step to grasping the Flex source code. Much of the Flex code is shared in key parent classes and it is important to understand this structure before delving into the details of a particular class in the framework.

The Flex 3 class hierarchy extends from various parent classes which begin with the name Flex* such as FlexSprite and FlexShape, which are subclasses of Sprite and Shape, respectively. These classes are very small and simply change the semantics of the name property to correspond to Flex's idea of the display list. For more about Sprite and Shape, see the Flash Physiology. From FlexSprite, the hierarchy goes to UIComponent which is the base class for all of the interactive classes in Flex.

UIComponent is the parent of the basic visual components such as Button, CheckBox, and ComboBox, as well as the parent of the more complicated classes such as Canvas, DataGrid, and Tree. UIComponent is such a monolithic class that it has its own section in the Anatomy.

FlexShape is the parent of non-interactive Flex components. This is limited to ProgrammaticSkin, which is the parent of Border and then RectangularBorder. See the section on Skinning for more details on these classes.