Block 的声明方式

原文链接：How Do I Declare A Block in Objective-C?

• 局部变量

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

• 属性

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

• 方法参数

  - (void)someMethodThatTakesABlock:(returnType (^nullability)(parameterTypes))blockName;

• 方法调用的参数

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

• C 函数的参数

  void SomeFunctionThatTakesABlock(returnType (^blockName)(parameterTypes));

• 类型定义

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