如何在Objective-C中声明一个Block？

接下来正文中出现词语定义:

returnType: 返回类型， NSInteger、BOOL、int、...
blockName: block名称，自己定义
parameterTypes: 参数类型 ，NSInteger、BOOL、int、...
parameters : 参数类型 +名 称 ，NSInteger index, BOOL flag ...
someObject : 对象，实例对象 、类对象、self、...

• 局部变量

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

NSInteger (^myblock)(BOOL) = ^NSInteger(BOOL flag) {
  //code
  if(flag) return 1
  return 0;
};

• 属性

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

@property (nonatomic,   copy) NSInteger (^myblock)(BOOL flag);

• 方法参数

-(void)someMethodWithBlock:(returnType(^)(parameters))blockName;

- (void)someMethodWithBlock:(NSInteger(^)(BOOL flag))myblock
{
     //code 
    NSInteger index = myblock(YES);
    //处理返回值 index
}

• 方法调用的参数

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

 [self someMethodWithBlock:^NSInteger(BOOL flag) {
    ///code
    if (flag) return 1;
    return 0;
}];

• C函数的参数：

  voidSomeFunctionWithBlock( returnType(^blockName)(parameterTypes));

  void someMethodWichBlock(NSInteger(^myblock)(BOOL)){
    //code 
   NSInteger index = myblock(YES);
    //处理返回值 index
  };    
  

• typedef：

typedef returnType (^blockName)(parameters);

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

typedef  NSInteger (Myblock)(BOOL flag);

//调用
 Myblock block = ^NSInteger(BOOL flag){
    //code
   if(flag)return 1;
   return 0;   
 };

参考:How Do I Declare A Block in Objective-C?