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。

使用标准的Cocoa命名和格式化约定和术语，而不是使用其他环境中使用的任何术语。有很多Cocoa开发人员，当他们中的另一个人开始使用您的代码时，如果它看起来和感觉上与其他Cocoa代码相似，那么它将更容易接近。

做什么和不做什么的例子:

Don't declare id m_something; in an object's interface and call it a member variable or field; use something or _something for its name and call it an instance variable. Don't name a getter -getSomething; the proper Cocoa name is just -something. Don't name a setter -something:; it should be -setSomething: The method name is interspersed with the arguments and includes colons; it's -[NSObject performSelector:withObject:], not NSObject::performSelector. Use inter-caps (CamelCase) in method names, parameters, variables, class names, etc. rather than underbars (underscores). Class names start with an upper-case letter, variable and method names with lower-case.

无论你做什么，不要使用Win16/ win32风格的匈牙利符号。甚至微软也在转向。net平台时放弃了这一点。

使用NSAssert和朋友。 我一直使用nil作为有效对象…特别是发送消息给nil在Obj-C中是完全有效的。 然而，如果我真的想确定一个变量的状态，我使用NSAssert和NSParameterAssert，这有助于轻松跟踪问题。

对于初学者来说，一个很明显的方法是:利用Xcode的自动缩进功能。即使是从其他源复制/粘贴代码，粘贴完代码后，也可以选择整个代码块，右键单击它，然后选择选项重新缩进该代码块中的所有内容。

Xcode会解析这个section并根据括号，循环等缩进它。这比每一行都按空格键或tab键要有效率得多。

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.

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)