When you build and save a user object, PowerBuilder treats the object as a unit that includes:
The object (and any controls within the object if it is a custom visual user object)
The object's properties, events, and scripts
Any variables, functions, or structures declared for the object
When you use inheritance to build a new user object, everything in the ancestor user object is inherited in the direct descendant and in its descendants in turn.
If you create a user object by inheriting it from a custom class or standard class user object that has public or protected instance variables with simple datatypes, the instance variables display and can be modified in the descendent user object’s Properties view.
All public instance variables with simple datatypes such as integer, boolean, character, date, string, and so on display in the descendant. Instance variables with the any or blob datatype or instance variables that are objects or arrays do not display.
You can do the following in a descendent user object:
Change the values of the properties and the variables
Build scripts for events that do not have scripts in the ancestor
Extend or override the inherited scripts
Add controls (in custom visual user objects)
Reference the ancestor's functions and events
Reference the ancestor’s structures if the ancestor contains a public or protected instance variable of the structure datatype
Access ancestor properties, such as instance variables, if the scope of the property is public or protected
Declare variables, events, functions, and structures for the descendant
In a descendent user object, you cannot delete controls inherited from a custom visual user object. If you do not need a control in a descendent user object, you can make it invisible.
The issues concerning inheritance with user objects are the same as the issues concerning inheritance with windows and menus. See Chapter 13, “Understanding Inheritance,” for more information.
