block语法

How Do I Declare A Block in Objective-C?

As a local variable:

1.
returnType (^blockName)(parameterTypes) = ^returnType(parameters) {...};

2.
@property (nonatomic, copy) returnType (^blockName)(parameterTypes);

3.
- (void)someMethodThatTakesABlock:(returnType (^)(parameterTypes))blockName;

4.
[someObject someMethodThatTakesABlock:^returnType (parameters) {...}];

5.
typedef returnType (^TypeName)(parameterTypes);
TypeName blockName = ^returnType(parameters) {...};