Built-in routines provide you with time-saving
ready-to-use encapsulated functionality whereas user-defined
routines provide you with the flexibility to define your own
routines when no built-in routine adequately contains the functionality
that you require.
Procedure
To determine whether to use a built-in or user-defined
routine:
- Determine what functionality you want the routine to encapsulate.
- Check the list of available built-in routines to see if
there are any that meet some or all of your requirements.
- If there is a built-in routine that meets some, but not all of
your requirements:
- Determine if the functionality that is missing, is functionality
that you can add simply to your application? If so, use the built-in
routine and modify your application to cover the missing functionality.
If the missing functionality is not easily added to your application
or if the missing functionality would have to be repeated in many
places consider creating a user-defined routine that contains the
missing functionality and that invokes the built-in routine.
- If you expect that your routine requirements will evolve and that
you might have to frequently modify the routine definition, consider
using a user-defined routine rather than the built-in routine.
- Determine if there are additional parameters that you might want
to pass into or out of the routine. If there are, consider creating
a user-defined routine that encapsulates an invocation to the built-in
routine.
- If no built-in routine adequately captures the functionality that
you want to encapsulate, create a user-defined routine.
Results
To save time and effort, whenever possible consider using
built-in routines. There will be times when the functionality that
you require will not be available within a built-in routine. For
these cases you must create a user-defined routine. Other times it
might be possible to include a call to built-in routine from a user-defined
routine that covers the extra functionality that you require.