About
objects
Contents
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.