iamthewalr.us

Development Tips (Issue 1)

Friday, March 7th, 2008

Recently, I’ve been collecting a bunch of best practices and style tips that I’ve been picking up. With ObjC2 and the iPhone SDK, the Cocoa landscape is changing quite rapidly, and a lot of my old conventions need to be updated and rethought given new modern tools.

Here’s a bunch of things I’ve found myself doing lately. I’ll try and write more of these down and publish them more often — positive feedback greatly appreciated. Thanks to the (now defunct) slerp iPhone tumblr blog for some of the inspiration.

• Try switching Xcode to use either the Midnight or Dusk color themes. On a computer screen, light text with a dark background is often easier to read than the other way around. Here’s a preview of Dusk:

  

  Isn’t that purdy?

• Look at using sigils on your member variables: i.e.:

  @interface Foo : NSOBject {
      NSArray *mFooArray;
  }
  - (void)addFoo;
  @end
  
  @implementation Foo
  - (void)addFoo
  {
      [mFoo addObject:[FooGetter retrieveFooFromFooLand]];
  }
  @end
  

  If you ever do access storage, you’ll know these are member variables. Same for static (sSomeStaticVar) and global (gEvilGlobalVariable). This is mitigated somewhat by Xcode’s highlighting (which I wish wasn’t so buggy — I filed this radar about it).

• If, on the other hand, you’re using ObjC2, and you’re using properties, use self.property as the accessor at all times. It Looks cleaner and is much less ambiguous. I still name my members with m sigils though, i.e.:

  @interface SwimmingPool : NSObject {
      float mDepth;
  }
  
  @property (nonatomic) float mDepth;
  
  - (BOOL)isItSafe;
  
  @end
  
  
  @implementation SwimmingPool
  
  @synthesize depth = mDepth;
  
  - (BOOL)isItSafe
  {
      // XXX Actually implement government safety standards... should be good for now though.
      return self.depth < 6.0f;
  }
  
  @end
  

  Not sure if I like this, but it definitely is more explicit and if I do need to access members directly, I know what I’m doing.

• Please please don’t use _ at the beginning of members or method names to mean “private.” That’s reserved by Apple, and I’ve had a collision on a method name bite me in the ass before. Granted, I figured it out pretty quick and renamed my method, but still. Don’t do it. Instead consider using m sigils for members. For “private” methods, I don’t really see much of a point to the _ prefix anyway — there’s no actual enforcement of this by anything. I have seen a few people postfix _ to private method names, i.e.

  - (void)somePrivateMethodWithArgs_:(id)arg andStuff:(id)arg2
  

  Not entirely sure how I feel about that. Comments welcome.

• Strings should probably be copy properties, i.e.

  @property (nonatomic, copy) NSString *label;
  

  If the copying becomes a bottleneck (which is possible on devices with limited amounts of memory, like a cell phone), you could remove it. I would advocate correctness over speed here — it’s better to be able to optimize later than have to hunt down weird bugs because you mutate something you shouldn’t have. Again, comments welcome either way — I’m certainly not adamant about this one quite yet.

• You may have noticed I’m using the nonatomic attribute for properties. This is because I’m working primarily in a “managed memory” (i.e., old school) environment. If you have switched to garbage collection, you should not include nonatomic — the documentation states that most of the time synthesized accessors in GC mode don’t require the type of overhead that the old-style ones do. That overhead appears to be a lock plus retain + autorelease. “Most of the time” is a pretty important caveat, by the way.

I’ve got a bunch more tips, but I’ve got to save something for issue 2!

I’m very open to feedback on any of these tips — feel free to comment if you don’t like what I’m doing, but I would ask that you briefly explain why your solution is better.