In object-oriented programming, an object is a self-contained module containing state information and associated methods. Most entities in PowerBuilder are objects: visual objects such as windows and controls on windows, nonvisual objects such as transaction and error objects, and user objects that you design yourself.
An object class is a definition of an object. You create an object’s definition in the appropriate painter: Window, Menu, Application, Structure, or User Object painter. In the painter, you add controls to be part of the object, specify initial values for the object’s properties, define its instance variables and functions, and write scripts for its events and functions.
An object instance is an occurrence of the object created during the execution of your application. Your code instantiates an object when it allocates memory for the object and defines the object based on the definition in the object class.
An object reference is your handle to the object instance. To interact with an object, you need its object reference. You can assign an object reference to a variable of the appropriate type.
There are two categories of objects supported by PowerBuilder: system objects (also referred to as system classes) defined by PowerBuilder and user objects you in define in painters.
System objects The PowerBuilder system objects or classes are inherited from the base class PowerObject. The system classes are the ancestors of all the objects you define. To see the system class hierarchy, select the System tab in the Browser, select PowerObject, and select Show Hierarchy and Expand All from the pop-up menu.
User objects You can create user object class definitions in several painters: Window, Menu, Application, Structure, and User Object painters. The objects you define are inherited from one of the system classes or another of your classes.
Some painters use many classes. In the Window and User Object painters, the main definition is inherited from the window or user object class. The controls you use are also inherited from the system class for that control.
