In PowerBuilder, a nonvisual user object can provide functionality similar to that of a structure. Its instance variables form a collection similar to the variables for the structure. In scripts, you use dot notation to refer to the user object’s instance variables, just as you do for structure variables.
The user object can include functions and its own structure definitions, and it allows you to inherit from an ancestor class. None of this is possible with a structure definition.
Memory allocation is different for user objects and structures. An object variable is a reference to the object. Declaring the variable does not allocate memory for the object. After you declare it, you must instantiate it with a CREATE statement. Assignment for a user object is also different (described in “Assignment for objects and structures”).
If you want a user object that has methods and inheritance but want the memory allocation of a structure, you can define an autoinstantiated object.
You do not have to create and destroy autoinstantiated objects. Like structures, they are created when they are declared and destroyed when they go out of scope. However, because assignment for autoinstantiated objects behaves like structures, the copies made of the object can be a drawback.
To make a custom class user object autoinstantiated, select the Autoinstantiate check box on the user object’s property sheet.
