抵制世界的子类化。在Cocoa中，很多工作都是通过委托和使用底层运行时完成的，而在其他框架中则是通过子类化完成的。

例如，在Java中你经常使用匿名*Listener子类的实例，在. net中你经常使用EventArgs子类。在Cocoa中，你什么都不用做——而是使用目标-动作。

这是一个微妙但很方便的方法。如果你将自己作为委托传递给另一个对象，在dealloc之前重置该对象的委托。

- (void)dealloc
{
self.someObject.delegate = NULL;
self.someObject = NULL;
//
[super dealloc];
}

这样做可以确保不再发送更多的委托方法。当您即将dealloc并消失在以太中时，您希望确保没有任何东西可以意外地向您发送更多消息。还记得自己。someObject可以被另一个对象保留(它可以是一个单例对象或在自动释放池中或其他任何对象)，直到您告诉它“停止向我发送消息!”，它才会认为您即将被释放的对象是公平的游戏。

养成这种习惯将使您避免大量令人痛苦的调试的奇怪崩溃。

同样的原理也适用于键值观察和NSNotifications。

编辑:

更有防御性的改变:

self.someObject.delegate = NULL;

成:

if (self.someObject.delegate == self)
    self.someObject.delegate = NULL;

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)

根据用户需要对字符串进行排序

在对要呈现给用户的字符串进行排序时，不应该使用简单的compare:方法。相反，你应该总是使用本地化比较方法，如localizedCompare:或localizedcaseinsensitiveecompare:。

有关详细信息，请参见搜索、比较和排序字符串。

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。