Correcting the Dots

One of the cool things about Objective-C is all the common conventions. My code should look like your code.

But there seems to be one area where we’ve decided that anarchy is okay.

I’m a wild fan of chaos and things-on-fire — everywhere except for code. So here are my two pleas:

  1. Use dot notation for properties.

  2. Do not use dot notation for non-properties.

Yes, I know it doesn’t matter to the compiled code, but I like having the conceptual difference, and the syntax reinforces that difference.

And while you might not like dot notation — or you might love it and want to use it for things like count that are not properties — I ask you to remember that cool thing about Cocoa where we care about readability and common conventions.

Searching

In case the appeal to principle didn’t do the trick for you, here’s a practical case.

Say I’m searching a .m file to find out where a UIImageView gets its image set. Knowing that image is a property, I search on .image = to find out where it gets set.

If I find nothing I start to freak out because it doesn’t make any sense. I check the xib file to re-confirm that there’s no image specified there. I make sure the image view isn’t a public property — it isn’t referenced somewhere else. I even search the project for valueForKey:@"imageView" to see if some other class has cheated to get a reference to the image view. But no.

I know that image view displays an image, and I know the image is set somewhere in that file — and I can’t figure out where.

And then, after wasting time and brain cells, I remember to search on setImage:. There it is.

The above has happened to me. So has the problem of searching for count] in order to find when an array was counted — and not finding it, and getting frustrated, until I remember to search for .count.

What’s the obvious thing to do, the easiest way to agree? Just do what the headers say. If it’s a property, treat it as such. If it’s not, don’t.

And when in doubt, look it up. (If you’re not willing to take a little extra time to do things correctly, then you should probably find another career.)

11 Jun 2012

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