ios block申明

局部变量
returnType (^blockName)(parameterTypes) = ^returnType(parameters) {...};
举例：

int (^completion)(int a) = ^int(int a){
// ...
};
属性
@property (nonatomic, copy, nullability) returnType (^blockName)(parameterTypes);
举例：

@property (nonatomic, copy, nonnull) int (^completion)(int);
方法形参

• (void)doSomethingWithBlock:(returnType (^nullability)(parameterTypes))blockName;
  举例：

• (void) doSomethingWithCompletion:(int (^_Nullable)(int))blockName;
  方法实参
  [someObject doSomethingWithBlock:^returnType (parameters) {...}];
  举例：

[a doSomethingWithCompletion:^int (int) {
// ...
}];
类型定义
typedef returnType (^TypeName)(parameterTypes);
TypeName blockName = ^returnType(parameters) {
// ...
};
举例：

typedef int (^Handler)(int);
Handler handler = ^int(int) {
// ...
};
最后，Enjoy yourself！

作者：coderanger
链接：https://www.jianshu.com/p/a1aa24693f2e
来源：简书
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