双括号方法语法。
我对某种类型的方法语法有疑问。
例如，我知道这是做什么的..
NSString *theString = [[NSString alloc]init...blablabla];
分配是在类上执行的（在本例中为 NSString），而 init 是在类的实例上执行的。
如果我们知道
[variable method];
，我也知道它是如何起作用的.. 该方法被执行在“变量”上，
如果我有
variable = [instance method];
“方法”方法，则在实例上执行并存储在变量中。
但是我迷失的是看起来像这样的东西。
[[CCDirector sharedDirector]something:parameter];
我不确定在哪里执行什么操作。
I have a question about a certain type of method syntax.
For example I know what this does ..
NSString *theString = [[NSString alloc]init...blablabla];
The alloc is performed on the class (NSString in this case) and the init is performed on the instance of the class..
If we have
[variable method];
I know how that functions too.. the method is performed on "variable"
if I have
variable = [instance method];
the "method" method is performed on instance and stored in variable..
But where I get lost is at something that looks like this ..
[[CCDirector sharedDirector]something:parameter];
I'm not sure what action is being performed where..
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[CCDirector共享Director]正在获取director的单例实例。然后，您将使用parameter调用something方法。这将类似于这样做[CCDirector sharedDirector]is getting the singleton instance of the director. Then you are calling thesomethingmethod withparameter. It would be similar to doing this[CCDirector共享Director]是CCDirector上的一个方法，并返回一些对象。很像[NSString alloc]。该行的其余部分调用返回的对象上的方法。[CCDirector sharedDirector]is a method onCCDirector, and returns some object. Much like[NSString alloc]. The rest of the line calls a method on the object that's returned.正如 @hspain 指出的，它是用于表示单例实例的约定。实际的 alloc/init 发生，并且仅在sharedDirector 内发生一次。
这里是有关 Objective-C 中单例模式的更多信息 。
As @hspain pointed out, its a convention used to denote a singleton instance. The actual alloc/init occurs, and is only occured once, within sharedDirector.
Here is more information on the singleton pattern in objective-c.
括号在任何地方的含义都相同。消息表达式
[object arg0:value arg1:value ...]将消息@selector(arg0:arg1:...)发送到object （它本身可以是一个消息表达式）。消息处理程序可以返回一个对象，因此消息表达式的值本身可以是另一个消息的接收者。嵌套这些表达式与嵌套函数调用相同：CCDirector_sharedDirector()实际上并不存在；它只是用于比较。请注意：
init并不是发送到 NSString 实例（事实并非如此，因为[NSString alloc]实际上返回一个 NSCFString），就是将init发送到[NSString alloc]的结果。如果您发现嵌套消息难以阅读，可以将它们分成多行或使用临时变量。
The brackets mean the same everywhere. The message expression
[object arg0:value arg1:value ...]sends the message@selector(arg0:arg1:...)toobject(which could itself be a message expression). The message handler can return an object, so the value of a message expression can itself be the recipient of another message. Nesting these expressions is the same as nesting function calls:CCDirector_sharedDirector()doesn't actually exist; it's just used for comparison.Note that in:
It's not so much that
initis sent to an NSString instance (it isn't, as[NSString alloc]actually returns an NSCFString), it's thatinitis sent to the result of[NSString alloc].If you find nested messages hard to read, you can break them into multiple lines or use temporary variables.