Terminology
The class information includes information about the relationships
between objects. These definitions will help you understand what the
information means.
object instance
A realization of an object. The instance exists in memory and has
values assigned to its properties and variables. Object instances exist
only when you run an application.
class
A definition of an object, containing the source code for creating
an object instance. When you use PowerBuilder painters and save an
object in a PBL, you are creating class definitions for objects. When
you run your application, the class is the datatype of object instances
based on that class. In PowerBuilder, the term object usually refers to
an instance of the object. It sometimes refers to an object’s
class.
system class
A class defined by PowerBuilder. An object you define in a painter
is a descendant of a system class, even when you do not explicitly
choose to use inheritance for the object you define.
parent
The object that contains the current object or is connected to the
object in a way other than inheritance. This table lists classes of
objects and the classes that can be the parents of those objects:
|
Object |
Parent |
|---|---|
|
Window |
The window that opened the window. A |
|
Menu item |
The menu item on the prior level in the The item on the menu bar is the parent of all |
|
Control on a window |
The window. |
|
Control on user object |
The user object. |
|
TabPage |
The Tab control in which the TabPage is defined or |
|
ListViewItem or TreeViewItem |
The ListView or TreeView control. |
|
Visual user object |
The window or user object on which the user object |
child
A class that is contained within another parent class. Also called
a nested class. For the types of objects that have a parent and child
relationship, see parent.
ancestor
A class from whose definition another object is inherited. See
also descendant.
descendant
An object that is inherited from another object and that
incorporates the specifics of that object: its properties, functions,
events, and variables. The descendant can use these values or override
them with new definitions. All objects you define in painters and store
in libraries are descendants of PowerBuilder system classes.
inheritance hierarchy
An object and all its ancestors.
collapsed hierarchy
A view of an object class definition that includes information
from all the ancestors in the object’s inheritance tree, not just items
defined at the current level of inheritance.
scalar
A simple datatype that is not an object or an array. For example,
Integer, Boolean, Date, Any, and String.
instance variable and
property
Built-in properties of PowerBuilder system objects are called
properties, but they are treated as instance variables in the class
definition information.