A class user object lets you reuse a set of business rules or other processing that acts as a unit but has no visual component. For example, you might define a class that calculates sales commissions or performs statistical analysis. Whenever you need to do this type of processing, you instantiate the user object in a script and call its functions.
You build class user objects in the User Object painter, specifying instance variables and object-level functions. Then you create an instance of the class user object in your application, thereby making its processing available.
There are two kinds of class user objects:
Custom class
Standard class
Custom class user objects are objects of your own design that encapsulate properties and functions not visible to the user. They are not derived from PowerBuilder objects. You define them to create units of processing that have no visual component.
For example, to calculate commissions in an application, you can define an n_CalculateCommission custom class user object that contains properties and user-defined functions that do the processing to calculate commissions.
Whenever you need to use this processing, you create an instance of the user object in a script, which then has access to the logic in the user object.
When you build components that you will deploy to a transaction server, you use custom class user objects. For more information, see Application Techniques.
A standard class user object inherits its definition from one built-in, nonvisual PowerBuilder object, such as the Transaction object or Error object. You modify the definition to make the object specific to your application, and optionally add instance variables and functions to enhance the behavior of the built-in object. Once you define a standard class user object, you can go to the Application painter and specify that you want to use it instead of the corresponding built-in system object in your application.
One important use of a standard class user object is employing one inherited from the built-in Transaction object to do database remote procedure calls from within an application.
