About objects
What an object is
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.
System objects versus user objects
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.