OC中声明Block的几种方式

1、作为局部变量


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


2、作为类的属性


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


3、方法参数


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


4、调用方法是传入的参数


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


5、自定义Block类型时


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