#import <Foundation/Foundation.h>
int main(int argc, const char * argv[]) {

    @autoreleasepool{

        /*

         Block是iOS中一種比較特殊的數據類型

         Block的作用

            -用來保存某一段代碼，可以在恰當的時間取出來調用

            -功能類似函數和方法

         Block和函數一樣，

         有返回值，有形參

         有返回值，沒形參

         無返回值，有形參

         無返回值，無形參

 */

        /*

         void代表block將來保存的代碼沒有返回值

         ()代表block將來保存的代碼沒有形參

         (^roseBlock)代表roseBlock是一個block變量，可以用于保存一段block代碼

  
      */

        void (^roseBlock)();

 
      roseBlock = ^{

            NSLog(@"roseBlock");

 
      };

        //調用block

 
      roseBlock();

  
     

 
  }

    return 0;

}

練習

#import <Foundation/Foundation.h>

 

int main(int argc, const char * argv[]) {

    @autoreleasepool{

 
 

        //先定義在初始化

        void (^numBlock)();

 
      numBlock = ^{

            NSLog(@"numBlock");

 
      };

 
      numBlock();

        //定義的同時初始化

        void (^Block)() = ^{

            NSLog(@"block");

 
      };

 
      Block();

  
     

        //無參有返回

        NSString *
(^StrBlock)()= ^{

            return [NSString stringWithFormat:@"StrBlock"];

 
      };

        NSLog(@"%@",StrBlock());

        //有參數有返回

        int (^sumBlock)(int ,int )= ^(int value1 ,int value2)

 
      {

            return value1+value2;

 
      };

        NSLog(@"sumBlock = %i",sumBlock(20,30));

  
     

        NSString
*(^stringBlock)(NSString*)= ^(NSString* str){

  
         

           NSString *s =  [NSString stringWithFormat:@"%@",str];

            NSLog(@"%@",s);

            return s;

 
      };

        stringBlock(@"lxc");

  
 

 
  }

    return 0;

}

 

用typedf給block起別名

#import <Foundation/Foundation.h>

typedef int(^calculate)(int,int);

int main(int argc, const char * argv[]) {

    @autoreleasepool{
          calculate sumBlock =^(int value1,int value2)
      {
            return value1 +value2;
      };

        NSLog(@"sumBlock =%i",sumBlock(20,10));
        calculate subBlock =^(int value1 ,int value2)

      {

            return value1 - value2;

 
      };

        NSLog(@"subBlock =%i",subBlock(20,10));

  }

    return 0;

}

 

Block的應用場景

#import <Foundation/Foundation.h>

void goToWorkDay1();

 

int main(int argc, const char * argv[]) {

    @autoreleasepool{
        goToWorkDay1();
  }

    return 0;

}

/*

  block的應用場景：前后都一樣中間不一樣的時候可以用block

  下面函數中void goToWork(void (^myBlock)())方法中包含一個block

  需要在當前方法中實現block

  在void goToWorkDay1()調用goToWork myblock會當做形參傳遞到函數中

 */

void goToWork(void (^myBlock)())

{

    NSLog(@"吃飯");

 
  myBlock();

    NSLog(@"睡覺");

}

 

void goToWorkDay1()

{

    goToWork(^{

        NSLog(@"敲代碼");

 
  });

}

void goToWokrDay2()

{

    goToWork(^{

        NSLog(@"打豆豆");

 
  });

}