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:

Table 4-1: Classes of objects and their parents

Object

Parent

Window

The window that opened the window.

A window might not have a parent. The parent is determined during execution and is not part of the class definition.

Menu item

The menu item on the prior level in the menu.

The item on the menu bar is the parent of all the items on the associated drop-down menu.

Control on a window

The window.

Control on user object

The user object.

TabPage

The Tab control in which the TabPage is defined or in which it was opened.

ListViewItem or TreeViewItem

The ListView or TreeView control.

Visual user object

The window or user object on which the user object is placed.

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.