不要忘记NSWindowController和NSViewController会释放它们所控制的NIB文件的顶级对象。

如果手动加载NIB文件，则在使用完该NIB的顶级对象后，需要负责释放它们。

确保您收藏了调试魔术页面。这应该是你在寻找Cocoa bug的源头时碰壁的第一站。

例如，它会告诉你如何找到你第一次分配内存的方法，后来导致崩溃(比如在应用程序终止期间)。

功能性更强。

Objective-C是面向对象的语言，但是Cocoa框架是函数式风格的，并且在很多情况下是函数式设计的。

There is separation of mutability. Use immutable classes as primary, and mutable object as secondary. For instance, use NSArray primarily, and use NSMutableArray only when you need. There is pure functions. Not so many, buy many of framework APIs are designed like pure function. Look at functions such as CGRectMake() or CGAffineTransformMake(). Obviously pointer form looks more efficient. However indirect argument with pointers can't offer side-effect-free. Design structures purely as much as possible. Separate even state objects. Use -copy instead of -retain when passing a value to other object. Because shared state can influence mutation to value in other object silently. So can't be side-effect-free. If you have a value from external from object, copy it. So it's also important designing shared state as minimal as possible.

但是也不要害怕使用不纯函数。

There is lazy evaluation. See something like -[UIViewController view] property. The view won't be created when the object is created. It'll be created when caller reading view property at first time. UIImage will not be loaded until it actually being drawn. There are many implementation like this design. This kind of designs are very helpful for resource management, but if you don't know the concept of lazy evaluation, it's not easy to understand behavior of them. There is closure. Use C-blocks as much as possible. This will simplify your life greatly. But read once more about block-memory-management before using it. There is semi-auto GC. NSAutoreleasePool. Use -autorelease primary. Use manual -retain/-release secondary when you really need. (ex: memory optimization, explicit resource deletion)

其中一些已经被提到过，但以下是我能想到的:

Follow KVO naming rules. Even if you don't use KVO now, in my experience often times it's still beneficial in the future. And if you are using KVO or bindings, you need to know things are going work the way they are supposed to. This covers not just accessor methods and instance variables, but to-many relationships, validation, auto-notifying dependent keys, and so on. Put private methods in a category. Not just the interface, but the implementation as well. It's good to have some distance conceptually between private and non-private methods. I include everything in my .m file. Put background thread methods in a category. Same as above. I've found it's good to keep a clear conceptual barrier when you're thinking about what's on the main thread and what's not. Use #pragma mark [section]. Usually I group by my own methods, each subclass's overrides, and any information or formal protocols. This makes it a lot easier to jump to exactly what I'm looking for. On the same topic, group similar methods (like a table view's delegate methods) together, don't just stick them anywhere. Prefix private methods & ivars with _. I like the way it looks, and I'm less likely to use an ivar when I mean a property by accident. Don't use mutator methods / properties in init & dealloc. I've never had anything bad happen because of it, but I can see the logic if you change the method to do something that depends on the state of your object. Put IBOutlets in properties. I actually just read this one here, but I'm going to start doing it. Regardless of any memory benefits, it seems better stylistically (at least to me). Avoid writing code you don't absolutely need. This really covers a lot of things, like making ivars when a #define will do, or caching an array instead of sorting it each time the data is needed. There's a lot I could say about this, but the bottom line is don't write code until you need it, or the profiler tells you to. It makes things a lot easier to maintain in the long run. Finish what you start. Having a lot of half-finished, buggy code is the fastest way to kill a project dead. If you need a stub method that's fine, just indicate it by putting NSLog( @"stub" ) inside, or however you want to keep track of things.

@kendell

而不是:

@interface MyClass (private)
- (void) someMethod
- (void) someOtherMethod
@end

Use:

@interface MyClass ()
- (void) someMethod
- (void) someOtherMethod
@end

Objective-C 2.0新功能。

Apple的Objective-C 2.0参考中描述了类扩展。

类扩展允许你在主类@interface块之外的位置为类声明额外的必需API

所以它们是实际类的一部分——而不是类之外的(私有)类别。细微但重要的区别。

IBOutlets

从历史上看，outlet的内存管理一直很差。 当前的最佳实践是将outlet声明为属性:

@interface MyClass :NSObject {
    NSTextField *textField;
}
@property (nonatomic, retain) IBOutlet NSTextField *textField;
@end

使用属性使内存管理语义清晰;如果使用实例变量综合，它还提供了一致的模式。