Block IOS 用法

1.理論

    Block (閉包):  A Block is an anonymous inline collection of code . and sometimes also called a "closure".

    閉包：能夠讀取其它函數內部變數的函數。

2.example

    1）TestBlock.h

     #import <Foundation/Foundation.h>

     typedef void(^Block)(void);
     typedef void(^Block_3)(void);
      int par;

    @interface TestBlock : NSObject
   {
     Block_3 block_3;
   }

  + (void)testBlock_1:(Block)_block;

  + (void)testBlock_2:(int(^)(int))_block;

  - (void)setBlock_3:(Block_3)newBlock;
  - (void)callBlock_3;

   @end

   2) TestBlock.m

    #import "TestBlock.h"

   @implementation TestBlock

    - (id)init
  {
      self = [super init];
      if (self) {
        
      }
    return self;
  }

+ (void)testBlock_1:(Block)_block;
{
    //回呼函數嘛，當然是要在函數內讓Block實現一次
    _block();
    NSLog(@"注意調用的順序");
}

+ (void)testBlock_2:(int(^)(int))_block
{
    int result = _block(par);
    NSLog(@"_______result:%d", result);
}

- (void)setBlock_3:(Block_3)newBlock
{
    [block_3 release];
    block_3 = [newBlock copy];
}

- (void)callBlock_3
{
    block_3();
}

- (void)dealloc
{
    [block_3 release], block_3 = nil;
    [super dealloc];
}

@end

3）調用

TestBlock *testBlock;

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    _testBlock = [[TestBlock alloc] init];
    
    /*==============================parting line==============================*/
    int (^myblock_1)(int a, int b) = ^(int a, int b){
        return a + b;
    };
    NSLog(@"------%d", myblock_1(1, 2));
    
    /*==============================parting line==============================*/
    //__block 變數
    __block int num;
    int (^myblock_2)(int a, int b) = ^(int a, int b){
        num = a + b;
        return num;
    };
    NSLog(@"++++++%d", myblock_2(2, 3));
    
    /*==============================parting line==============================*/
    //Block實現回調
    self.button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    self.button.frame = CGRectMake(100, 100, 100, 50);
    [self.button setTitle:@"TEST" forState:UIControlStateNormal];
    [self.button addTarget:self action:@selector(test:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.button];
    
    /*==============================parting line==============================*/
    //Block傳遞函數指標
    int (^test_1)()= ^{
        NSLog(@"I");
        return 1;
    };
    int (^test_2)()= ^{
        NSLog(@"MANNA");
        return 2;
    };
    int (^test_3)()= ^{
        NSLog(@"PLAY");
        return 3;
    };
    [self testBlock:test_1];
    [self testBlock:test_2];
    [self testBlock:test_3];
    
    /*==============================parting line==============================*/
    //多Block參數
    [self testBlock_Concurrency:^{
        NSLog(@"這是第一個Block.");
        return 100;
    }block_2:^(int p){
        NSLog(@"這是第二個Block.");
    }block_3:^{
        NSLog(@"這是第三個Block.");
    }];
}

- (void)test:(id)sender
{    
    [TestBlock testBlock_1:^{
        NSLog(@"FUCK U MAN.");
    }];
    
    //使用類方法實現調用
    par = 100;
    [TestBlock testBlock_2:^(int par){
        NSLog(@"++++++++++");
        return par - 1;
    }];
    
    //使用執行個體方法實現調用
    [self.testBlock setBlock_3:^{
         NSLog(@"this is block_3.");
    }];
    [self.testBlock callBlock_3];
}

- (void)testBlock:(int (^)())test_block
{
    int result = test_block();
    NSLog(@"注意先後順序，結果是:%d", result);
}

- (void)testBlock_Concurrency:(int (^)())block_1 block_2:(void(^)(int))block_2 block_3:(void(^)())block_3
{
    int result = block_1();
    block_2(100);
    block_3();
    
    NSLog(@"多麼神奇的Block.result=%d.", result);
}

4）測試結果 

2013-05-08 10:26:30.309 TEST_test_01[571:11303] ------3
2013-05-08 10:26:30.310 TEST_test_01[571:11303] ++++++5
2013-05-08 10:26:30.312 TEST_test_01[571:11303] I
2013-05-08 10:26:30.312 TEST_test_01[571:11303] 注意先後順序，結果是:1
2013-05-08 10:26:30.313 TEST_test_01[571:11303] MANNA
2013-05-08 10:26:30.313 TEST_test_01[571:11303] 注意先後順序，結果是:2
2013-05-08 10:26:30.314 TEST_test_01[571:11303] PLAY
2013-05-08 10:26:30.314 TEST_test_01[571:11303] 注意先後順序，結果是:3
2013-05-08 10:26:30.314 TEST_test_01[571:11303] 這是第一個Block.
2013-05-08 10:26:30.315 TEST_test_01[571:11303] 這是第二個Block.
2013-05-08 10:26:30.315 TEST_test_01[571:11303] 這是第三個Block.
2013-05-08 10:26:30.316 TEST_test_01[571:11303] 多麼神奇的Block.result=100.

2013-05-08 10:26:47.200 TEST_test_01[571:11303] FUCK U MAN.
2013-05-08 10:26:47.200 TEST_test_01[571:11303] 注意調用的順序
2013-05-08 10:26:47.201 TEST_test_01[571:11303] ++++++++++
2013-05-08 10:26:47.201 TEST_test_01[571:11303] _______result:99
2013-05-08 10:26:47.201 TEST_test_01[571:11303] this is block_3.