About user-defined functions

The PowerScript language has many built-in functions, but you may find that you need to code the same procedure over and over again. For example, you may need to perform a certain calculation in several places in an application or in different applications. In such a situation, create a user-defined function to perform the processing.

A user-defined function is a collection of PowerScript statements that perform some processing. After you define a user-defined function and save it in a library, any application accessing that library can use the function.

There are two kinds of user-defined functions, global and object-level functions.

Global functions

Global functions are not associated with any object in your application and are always accessible anywhere in the application.

They correspond to the PowerBuilder built-in functions that are not associated with an object, such as the mathematical and string-handling functions. You define global functions in the Function painter.

Object-level functions

Object-level functions are defined for a window, menu, user object, or application object. These functions are part of the object's definition and can always be used in scripts for the object itself. You can choose to make these functions accessible to other scripts as well.

These functions correspond to built-in functions that are defined for specific PowerBuilder objects such as windows or controls. You define object-level functions in a Script view for the object.

Deciding which kind you want

When you design your application, you need to decide how you will use the functions you will define:

  • If a function is general purpose and applies throughout an application, make it a global function.

  • If a function applies only to a particular kind of object, make it an object-level function. You can still call the function from anywhere in the application, but the function acts only on a particular object type.

    For example, suppose you want a function that returns the contents of a SingleLineEdit control in one window to another window. Make it a window-level function, defined in the window containing the SingleLineEdit control. Then, anywhere in your application that you need this value, call the window-level function.

Multiple objects can have functions with the same name

Two or more objects can have functions with the same name that do different things. In object-oriented terms, this is called polymorphism. For example, each window type can have its own Initialize function that performs processing unique to that window type. There is never any ambiguity about which function is being called, because you always specify the object's name when you call an object-level function.

Object-level functions can also be overloaded—two or more functions can have the same name but different argument lists. Global functions cannot be overloaded.