Objective-C Block
OC中block的语法实在是太别扭了，不知道是不是我太孤陋寡闻了。。。在此记录一下，以供日后查找使用。
引用：http://goshdarnblocksyntax.com
As a local variable:
returnType (^blockName)(parameterTypes) = ^returnType(parameters) {...};
As a property:
@property (nonatomic, copy, nullability) returnType (^blockName)(parameterTypes);
As a method parameter:
- (void)someMethodThatTakesABlock:(returnType (^)(parameterTypes))blockName;
As an argument to a method call:
[someObject someMethodThatTakesABlock:^returnType (parameters) {...}];
As a typedef:
typedef returnType (^TypeName)(parameterTypes);
TypeName blockName = ^returnType(parameters) {...};