Class user objects – PB Docs 2019

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 user
objects

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
the section called “Using Transaction Objects” in Application Techniques.

Standard class user
objects

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.