Rapid Application Development / Advanced Excel Development

VBA Best Practice

There is a lot of information floating around about how to get various things done in VBA, how to make the best use, or sometimes just the most use of VBA and Excel.
This section aims to add an element of Quality and Best Practices. These are just general guidelines, a professional developer will always assess the options and make the appropriate choice in their specific situation.
These suggestions are specific to Excel VBA in commercial settings, many will not translate to other technologies or other settings.

VBA Best Practice Series

High Quality Code - Procedures

• Consider the anatomy of a procedure/object - initialisation, process, clear up, error handling
• Short routines 40-50 lines max (one screens worth) (easier to understand - but not proven to reduce errors)
• A procedure should do one thing well
• Prefer functions (Boolean success/failure)
• Use parameters rather than global variables (max 7+/- 2)
• Avoid application.run - breaks VBA error handling
• Use separate routines for separate error handling
• Consider error handling early, use break on all errors when testing
• Use environ rather than api where possible (simple)
• All call tree parents should have error handling
• Test performance don't guess (see perfmon)
• Protect procedures from bad input (including malicious input)