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Issue 2.5

COLUMN

Design Eye for the Programming Guy

Rethinking the PopupMenu Interface

Issue: 2.5 (May/June 2004)
Author: Charles Yeomans
Author Bio: Charles Yeomans is a software developer in Lexington, Kentucky.
Article Description: No description available.
Article Length (in bytes): 5,154
Starting Page Number: 35
Article Number: 2517
Related Link(s): None

Excerpt of article text...

Let's consider a familiar example, the PopupMenu class. PopupMenu.ListIndex returns the index of the selected row, if one has been selected; otherwise it returns -1. Perhaps this seems like a reasonable, even natural design. I claim that it is not.

The problem is that PopupMenu.ListIndex is telling you two things; first, whether or not a menu item has been selected, and, second, the index of the selected row, if a row has been selected. It does this through the use of a magic value; that is, it returns -1 to signify that no row has been selected. The result is code like this:

If PopupMenu1.ListIndex > -1 then

...End of Excerpt. Please purchase the magazine to read the full article.