HOWTO: Use Optional Arguments in Intrinsic Data Types

• Microsoft Visual Basic Professional and Enterprise Editions for Windows, version 5.0

SUMMARY

One of the new features of Microsoft Visual Basic 5.0 and VBA 5.0 is the ability to define Optional arguments for data types other than Variant. These optional arguments are used in procedures.

MORE INFORMATION

Microsoft Visual Basic and VBA 5.0 allows optional arguments for the following data types:

   Data type
   ---------
   Currency
   Double
   Integer
   Long
   Single
   String
   Object

1. The Optional argument must be capable of being assigned a default value. When a procedure that has Optional arguments is called, Microsoft Visual Basic 5.0 assigns all arguments that were not included with a default value. Thus, an Optional array is not possible.

2. Optional arguments of user-defined data types are not supported. Microsoft Visual Basic 5.0 only supports Optional arguments of intrinsic data types.

3. Optional arguments that are of intrinsic data types always return False when used with the IsMissing function. This occurs because the IsMissing function is explicitly designed for un-initialized Variant data types. Because an intrinsic Optional argument always gets its default value if not passed to the procedure, it is never missing.

4. Applications written with earlier versions of Visual Basic for Applications will ignore the Optional modifier, and thus require the argument(s). A good example of this is Microsoft Access for Windows 95.

REFERENCES

Microsoft Visual Basic Online Help