evanseries.org

Brent Simmons just put a post up on his design philosophy for category methods, in which he presents the following rule:

If something is used just once, don’t make a category for it, just make it a static C function. Unless it’s big.

His reasoning is as follows:

1. Less code to maintain. (And, in this case, two fewer files: one deleted .h and one deleted .m.)
2. The code appears where it’s used: no need to jump to it if I need to edit it.

I’ve had this rule for a while, as well, and I think it’s a good one. But I have a third reason for employing it: if you’re only using a method in once place, you have no idea how it’s going to generalize. Maybe you can reuse it, as-is, in many other places. Perhaps it will need to be decomposed.

But trying to figure this stuff out the first time you need the functionality is a waste of time, because you’re likely to guess wrong. It’s better to save your energy for when you don’t have to guess at all: the second time (or the third time, or the fourth time) that the problem shows up, when you can refactor your way to a truly general solution.

Tags: cocoa, code, design, reply

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