Overloading Routines for Types in a Type Hierarchy

Routine overloading refers to the ability to assign one name to multiple routines and specify different types of arguments on which the routines can operate. In a type hierarchy, a subtype automatically inherits the routines that are defined on its supertype. However you can define a new routine on a subtype to override the inherited routine with the same name. For example, suppose you create a getinfo() routine on type person_t that returns the last name and birthdate of an instance of type person_t. You can register another getinfo() routine on type employee_t that returns the last name and salary from an instance of employee_t. In this way, you can overload a routine, so that you have a customized routine for every type in the type hierarchy, as Figure 30 shows.

Figure 30. Example of Routine Overloading in a Type Hierarchy

When you overload a routine so that routines are defined with the same name but different arguments for different types in the type hierarchy, the argument that you specify determines which routine executes. For example, if you call getinfo() with an argument of type employee_t, a getinfo() routine defined on type employee_t overrides the inherited routine of the same name. Similarly, if you define another getinfo() on type sales_rep_t, a call to getinfo() with an argument of type sales_rep_t overrides the routine that sales_rep_t inherits from employee_t.

For information about how to create and register user-defined routines (UDRs), see IBM Informix: User-Defined Routines and Data Types Developer's Guide.