Block小常识

作为苹果推荐的一种数据回调方式和数据类型,Block经常在项目中使用,但又经常忘记它特有的写法,所以专门做个小笔记,备查.

1.作为局部变量

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

2.作为属性

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

3.作为方法参数

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

4.作为回调参数

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

5.typedef的简写

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

6.self的弱引用(防止循环引用)

__weak typeof(self) weakSelf = self;

7.修改局部变量

__block NSString *someString = @"can be changed by Block";