zani的博客

  id foo1; NSObject *foo2; id<NSObject> foo3;     The first one is the most common.It simply declares a pointer to some Objective-C object (see /usr/include/objc/objc.h). id gives the...

转自:http://haoxiang.org/2011/08/ios-delegate-and-protocol/ protocol和delegate完全不是一回事，放在一起说，只是因为我们经常在同一个头文件里看到这两个word。 protocol和java里interface的概念类似，是Objective-C语法的一部分。定义protocol如下 @protocol Cla...

Directly from Apple: "The NSNull class defines a singleton object you use to represent null values in situations where nil is prohibited as a value (typically in a collection object such as an array o...