Evolution of a Function: ShowForm()

This is the introduction to a series on the evolution of my ShowForm() function.

• Part 1: Minimum Viable Product (MVP)
• Part 2: Multiple Form Instance Support
• Parts 3+: (Not yet published)

There are 4 keys to building generic solutions in code:

1. Avoid premature generalization by sticking to the Rule of Thrice
2. Make sure any additional time spent building a generic solution is worth it
3. Build only what you need at first; don't try to anticipate future use cases
4. Maintain backward compatibility as you add features

To illustrate points 3 and 4, I'm going to take you with me on a journey through the development of one of the foundational building blocks of my Access applications: my ShowForm() function.

The ShowForm() Function

At its most basic, the ShowForm function acts as a wrapper around the built-in DoCmd.OpenForm method.

Over time, the function grew to encompass the following features:

• Simplify calling code by eliminating the View and FilterName arguments
• Avoid "Syntax error (missing operator) in query expression 'MyField = '." errors
• Force-apply new filter criteria to already-open forms*
• Restore the form being opened if it is currently minimized*
• Reveal the form being opened if it is currently hidden*
• Support multiple form instances with no change to the calling code
• Avoid creating duplicate form instances (based on WhereCondition and OpenArgs arguments)
• Automatically cascade multi-instance forms (to avoid obscuring other instances of the same form)
• Return the window handle of the newly opened form (to track specific instances of a multi-instance form)

^{*NOTE: Features with asterisks in the list above appear to be built into the latest versions of Access, though I swear they were missing in earlier versions (e.g., Access 2000).}

Through a series of follow-up articles, I will show you how this function evolved and grew over a period of several years.  

From its humble beginnings to its current grandeur, this function is a great example of the power of Just-In-Time development mixed with reverence for backwards compatibility.

The Value of Version Control

I should point out the thing that makes this article series possible is my long and consistent use of version control to maintain my code library:

Without version control, I'd be able to show you the code for the function as it is now, but I would have no way to show you how it evolved over time.  Being able to see how code evolves is a powerful way to gain insight into why a piece of code works the way it does.

Image modified from Wheel of Fortune template on Kapwing.com