多線程Operation

  • NSOperation的作用
    • 配合使用NSOperation和NSOperationQueue也能實(shí)現(xiàn)多線程編程
    • NSOperation和NSOperationQueue實(shí)現(xiàn)多線程的具體步驟
    • 先將需要執(zhí)行的操作封裝到一個(gè)NSOperation對(duì)象中
    • 然后將NSOperation對(duì)象添加到NSOperationQueue中
    • 系統(tǒng)會(huì)自動(dòng)將NSOperationQueue中的NSOperation取出來(lái)
    • 將取出的NSOperation封裝的操作放到一條新線程中執(zhí)行
  • NSOperation的子類
    • NSInvocationOperation
    • NSBlockOperation
    • 自定義子類繼承NSOperation，實(shí)現(xiàn)內(nèi)部相應(yīng)的方法

1. NSInvocationOperation

- (void)InvocationOperation{
     // 1.創(chuàng)建操作, 封裝任務(wù)
      /*
       第一個(gè)參數(shù): 目標(biāo)對(duì)象, self
       第二個(gè)參數(shù): 調(diào)用方法的名稱
       第三個(gè)參數(shù): 前面方法需要接收的參數(shù) nil
       */
      NSInvocationOperation *op1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(run1) object:nil];
      NSInvocationOperation *op2 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(run2) object:nil];
      NSInvocationOperation *op3 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(run3) object:nil];
    // 2.創(chuàng)建隊(duì)列
    /*
      GCD的隊(duì)列類型:
        串行類型: create & 主隊(duì)列
        并發(fā)類型: create & 全局并發(fā)隊(duì)列
     
      NSOperation:
        主隊(duì)列: [NSOperationQueue mainQueue]和GCD的主隊(duì)列一樣, 串行隊(duì)列
        非主隊(duì)列: [[NSOperationQueue alloc] init] 非常特殊(同時(shí)具備串行和并發(fā)的功能)
        默認(rèn)情況下, 非主隊(duì)列是并發(fā)隊(duì)列
     */
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    
    [queue addOperation:op1];
    [queue addOperation:op2];
    [queue addOperation:op3];
    

}   

- (void)run1{
    NSLog(@"%@", [NSThread currentThread]);
}

- (void)run2{
    NSLog(@"%@", [NSThread currentThread]);
}
- (void)run3{
    NSLog(@"%@", [NSThread currentThread]);
}

2. NSBlockOperation

- (void)blockOperation{
    NSBlockOperation *op = [NSBlockOperation blockOperationWithBlock:^{
    // 在主線程
    NSLog(@"__%@", [NSThread currentThread]);
 }];

// 添加額外的任務(wù)(在子線程中執(zhí)行)
    [op addExecutionBlock:^{
        NSLog(@"下載2__%@", [NSThread currentThread]);
  }];

   [op addExecutionBlock:^{
    NSLog(@"下載3__%@", [NSThread currentThread]);
  }];

   [op addExecutionBlock:^{
    NSLog(@"下載4__%@", [NSThread currentThread]);
  }];

  [op start];
}

打印結(jié)果

<NSThread: 0x600000260ec0>{number = 5, name = (null)}
下載2__<NSThread: 0x60800007b900>{number = 1, name = main}
下載4__<NSThread: 0x60000007bf80>{number = 7, name = (null)}
下載3__<NSThread: 0x600000261600>{number = 6, name = (null)}

可以看出如果一個(gè)操作(一個(gè)NSBLockOperation對(duì)象)中的任務(wù)數(shù)量大于1, 那么會(huì)開(kāi)子線程執(zhí)行并發(fā)任務(wù)

把NSOperation對(duì)象添加到NSOperationQueue中

- (void)blockOperation{
 
 NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{
     NSLog(@"op1---%@", [NSThread currentThread]);
 }];
 
 [op1 addExecutionBlock:^{
     NSLog(@"下載1__%@", [NSThread currentThread]);
 }];
 
 [op1 addExecutionBlock:^{
     NSLog(@"下載2__%@", [NSThread currentThread]);
 }];
 
 [op1 addExecutionBlock:^{
     NSLog(@"下載3__%@", [NSThread currentThread]);
 }];
 
 NSBlockOperation *op2 = [NSBlockOperation blockOperationWithBlock:^{
     NSLog(@"op2---%@", [NSThread currentThread]);
 }];

 NSBlockOperation *op3 = [NSBlockOperation blockOperationWithBlock:^{
     NSLog(@"op3---%@", [NSThread currentThread]);
 }];
 
 
 NSOperationQueue *queue = [[NSOperationQueue alloc] init];
 [queue addOperation:op1];
 [queue addOperation:op2];
 [queue addOperation:op3];

// 簡(jiǎn)便方法 1.創(chuàng)建操作 2.將操作添加到隊(duì)列中
 [queue addOperationWithBlock:^{
     NSLog(@"addOperationWithBlock---%@", [NSThread currentThread]);
 }];

 
}

op2---<NSThread: 0x60800007ff00>{number = 4, name = (null)}
op1---<NSThread: 0x608000078080>{number = 3, name = (null)}
下載1__<NSThread: 0x608000272dc0>{number = 5, name = (null)}
addOperationWithBlock---<NSThread: 0x608000262e00>{number = 7, name = (null)}
op3---<NSThread: 0x600000279080>{number = 6, name = (null)}
下載2__<NSThread: 0x608000078080>{number = 3, name = (null)}
下載3__<NSThread: 0x60800007ff00>{number = 4, name = (null)}

打印結(jié)果顯示也是并發(fā)執(zhí)行的
如果使用blockOperationWithBlock和NSInvocationOperation創(chuàng)建的操作中代碼非常多, 可以使用自定義的子類繼承NSOperation, 實(shí)現(xiàn)內(nèi)部的main方法。
好處和其他的自定義控件一樣有利于代碼隱藏和提高代碼復(fù)用性。

上面說(shuō)到非主隊(duì)列, 即[[NSOperationQueue alloc] init]創(chuàng)建的隊(duì)列默認(rèn)情況下是并發(fā)隊(duì)列, 怎么讓它變成串行隊(duì)列呢:

- (void)maxConrurrentOperationCount{
 NSOperationQueue *queue = [[NSOperationQueue alloc] init];
 
 // 設(shè)置并發(fā)數(shù)量maxConcurrentOperationCount(同一時(shí)間最多有多少個(gè)任務(wù)在執(zhí)行)
 // static const NSInteger NSOperationQueueDefaultMaxConcurrentOperationCount = -1;系統(tǒng)默認(rèn)為-1, 特殊意義  最大值 表示不受限制

 queue.maxConcurrentOperationCount = 3;
 
 for (int i = 0; i < 10; i++) {
     NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
         NSLog(@"i=%d, %@", i,[NSThread currentThread]);
     }];
     [queue addOperation:operation];
 }
}

打印結(jié)果

 i=0, <NSThread: 0x60800007e180>{number = 5, name = (null)}
 i=1, <NSThread: 0x600000260c00>{number = 6, name = (null)}
 i=2, <NSThread: 0x600000278e00>{number = 7, name = (null)}
 i=3, <NSThread: 0x60800007e180>{number = 5, name = (null)}
 i=4, <NSThread: 0x600000260c00>{number = 6, name = (null)}
 i=5, <NSThread: 0x600000278e00>{number = 7, name = (null)}
 i=6, <NSThread: 0x60800007e180>{number = 5, name = (null)}
 i=7, <NSThread: 0x600000260c00>{number = 6, name = (null)}
 i=8, <NSThread: 0x600000278e00>{number = 7, name = (null)}
 i=9, <NSThread: 0x60800007e180>{number = 5, name = (null)}

可以看出只開(kāi)了3條線程并發(fā)執(zhí)行
如果設(shè)置maxConcurrentOperationCount = 5

 i=0, <NSThread: 0x60800006c300>{number = 3, name = (null)}
 i=1, <NSThread: 0x60000006eb40>{number = 5, name = (null)}
 i=2, <NSThread: 0x600000070800>{number = 6, name = (null)}
 i=3, <NSThread: 0x60000007e940>{number = 7, name = (null)}
 i=4, <NSThread: 0x608000262c40>{number = 8, name = (null)}
 i=5, <NSThread: 0x60800006c300>{number = 3, name = (null)}
 i=6, <NSThread: 0x60000006eb40>{number = 5, name = (null)}
 i=7, <NSThread: 0x600000070800>{number = 6, name = (null)}
 i=8, <NSThread: 0x60000007e940>{number = 7, name = (null)}
 i=9, <NSThread: 0x608000262c40>{number = 8, name = (null)}

可以看出只開(kāi)了5條線程并發(fā)執(zhí)行
ps 串行隊(duì)列的特點(diǎn)是同一時(shí)間只有一個(gè)任務(wù)在執(zhí)行, 所以只要把maxConcurrentOperationCount設(shè)置為1就可以了

 i=0, <NSThread: 0x60000007a680>{number = 3, name = (null)}
 i=1, <NSThread: 0x60000007a680>{number = 3, name = (null)}
 i=2, <NSThread: 0x60000007a680>{number = 3, name = (null)}
 i=3, <NSThread: 0x60000007a680>{number = 3, name = (null)}
 i=4, <NSThread: 0x6080002667c0>{number = 4, name = (null)}
 i=5, <NSThread: 0x6080002667c0>{number = 4, name = (null)}
 i=6, <NSThread: 0x6080002667c0>{number = 4, name = (null)}
 i=7, <NSThread: 0x6080002667c0>{number = 4, name = (null)}
 i=8, <NSThread: 0x6080002667c0>{number = 4, name = (null)}
 i=9, <NSThread: 0x6080002667c0>{number = 4, name = (null)}

當(dāng)設(shè)置masConcurrentOperationCount = 1時(shí), 開(kāi)啟了兩條線程串行執(zhí)行任務(wù), 串行隊(duì)列是按照FIFO順序執(zhí)行任務(wù), 而不是只開(kāi)啟一條線程

隊(duì)列的狀態(tài): 隊(duì)列中的任務(wù)也是有狀態(tài)的: 已經(jīng)執(zhí)行完畢的 | 正在執(zhí)行 | 隊(duì)列等待狀態(tài)

  1. 暫停[queue setSuspended:YES], 可以恢復(fù)繼續(xù)執(zhí)行[queue setSuspended:NO], 不能暫停正在繼續(xù)執(zhí)行的任務(wù)
  2. 取消[queue cancelAllOperations];, 不可以恢復(fù)
如何取消自定義Operation
新建類繼承NSOPeration
// 自定義Operation只要重寫(xiě)main方法就可以了
- (void)main{
    
    for (int i = 0; i < 1000; i ++) {
        NSLog(@"download1----%d-----%@", i , [NSThread currentThread]);
    }
    
    for (int i = 0; i < 1000; i ++) {
        NSLog(@"download2----%d-----%@", i , [NSThread currentThread]);
    }

    
    for (int i = 0; i < 1000; i ++) {
        NSLog(@"download3----%d-----%@", i , [NSThread currentThread]);
    }

}

@property (nonatomic, strong) NSOperationQueue *operationQueue;

- (void)viewDidLoad
{

    self.operationQueue = [[NSOperationQueue alloc] init];
    
    CustomOperation *operation = [[CustomOperation alloc] init];
    
    [self.operationQueue addOperation:operation];
    
}

- (IBAction)cancell:(id)sender {
    [self.operationQueue cancelAllOperations];
}

現(xiàn)在點(diǎn)擊取消執(zhí)行cancell方法并沒(méi)有效果, 它會(huì)將三個(gè)for循環(huán)都打印完, 如果我想執(zhí)行完download1任務(wù)后可以這么做:

- (void)main{
    
    for (int i = 0; i < 1000; i ++) {
        NSLog(@"download1----%d-----%@", i , [NSThread currentThread]);
    }
    if (self.isCancelled) return;
    
    
    for (int i = 0; i < 1000; i ++) {
        NSLog(@"download2----%d-----%@", i , [NSThread currentThread]);
    }
    if (self.isCancelled) return;
    
    
    for (int i = 0; i < 1000; i ++) {
        NSLog(@"download3----%d-----%@", i , [NSThread currentThread]);
    }
    if (self.isCancelled) return;

}
NSOperation操作依賴
用NSOperation和NSOperationQueue處理a, b, c三個(gè)線程, 要求執(zhí)行完a, b后才能執(zhí)行c, 改怎么做?
    // 創(chuàng)建隊(duì)列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    
   // 創(chuàng)建3個(gè)操作  1個(gè)NSOperation對(duì)應(yīng)一個(gè)線程   
    NSOperation *a = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"operation-----a");
    }];
    
    NSOperation *b = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"operation-----b");
    }];

    NSOperation *c = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"operation-----c");
    }];
    
    
    // 添加依賴
    [c addDependency:a];  // 只有當(dāng)a操作執(zhí)行完, 才會(huì)執(zhí)行c操作
    [c addDependency:b];  // 只有當(dāng)b操作執(zhí)行完, 才會(huì)執(zhí)行c操作
    
    // 執(zhí)行操作    應(yīng)該先添加依賴才添加到隊(duì)列(addOperation)里面去, 因?yàn)橐坏┨砑拥疥?duì)列就開(kāi)始創(chuàng)建線程, 執(zhí)行相關(guān)線程的方法
    [queue addOperation:a];
    [queue addOperation:b];
    [queue addOperation:c];

結(jié)果

operation-----b
operation-----a
operation-----c

不能相互依賴, 即 [c addDependency:a];[a addDependency:c];如果這樣寫(xiě), 也不會(huì)崩潰, 而是誰(shuí)都不執(zhí)行

也可以兩個(gè)跨隊(duì)列(NSOperationQueue)依賴

// 跨隊(duì)列依賴
- (void)dependency1{
    // 創(chuàng)建隊(duì)列
    NSOperationQueue *queueA = [[NSOperationQueue alloc] init];
    NSOperationQueue *queueB = [[NSOperationQueue alloc] init];
    
    // 創(chuàng)建3個(gè)操作  1個(gè)NSOperation對(duì)應(yīng)一個(gè)線程
    NSOperation *a = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"operation-----a");
    }];
    
    NSOperation *b = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"operation-----b");
    }];
    
    NSOperation *c = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"operation-----c");
    }];
    
    
    // 添加依賴
    [c addDependency:a];  // 只有當(dāng)a操作執(zhí)行完, 才會(huì)執(zhí)行c操作
    [c addDependency:b];  // 只有當(dāng)b操作執(zhí)行完, 才會(huì)執(zhí)行c操作
    
    // 執(zhí)行操作    應(yīng)該先添加依賴才添加到隊(duì)列(addOperation)里面去, 因?yàn)橐坏┨砑拥疥?duì)列就開(kāi)始創(chuàng)建線程, 執(zhí)行相關(guān)線程的方法
    [queueA addOperation:a];
    [queueB addOperation:b];
    [queueB addOperation:c];
}

結(jié)果也是一樣的

operation-----b
operation-----a
operation-----c
NSOperation監(jiān)聽(tīng)

可能會(huì)有這樣一種場(chǎng)景, 比如下載電影, 我希望在電影下載完以后通知一下用戶, 這時(shí)候就需要NSOPeration監(jiān)聽(tīng)

- (void)completion{
    // 創(chuàng)建隊(duì)列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    
    // 創(chuàng)建3個(gè)操作  1個(gè)NSOperation對(duì)應(yīng)一個(gè)線程
    NSBlockOperation *a = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"operation-----a, %@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *b = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"operation-----b, %@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *c = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"operation-----c, %@", [NSThread currentThread]);
    }];
    
    c.completionBlock = ^{
        NSLog(@"c操作完成 %@", [NSThread currentThread]);
    };
    
    
    [queue addOperation:a];
    [queue addOperation:b];
    [queue addOperation:c];
}

 operation-----a, <NSThread: 0x608000264640>{number = 4, name = (null)}
 operation-----b, <NSThread: 0x6080000725c0>{number = 8, name = (null)}
 operation-----c, <NSThread: 0x60800007d6c0>{number = 3, name = (null)}
 c操作完成 <NSThread: 0x60800007d6c0>{number = 3, name = (null)}

NSOperation線程通訊

- (void)viewDidLoad
{
    NSOperationQueue *operationQueue = [[NSOperationQueue alloc] init];
    
    NSOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
       
        NSURL *url = [NSURL URLWithString:@"https://image.baidu.com/search/detail?ct=503316480&z=0&ipn=d&word=王者榮耀&step_word=&hs=0&pn=5&spn=0&di=64062655030&pi=0&rn=1&tn=baiduimagedetail&is=0%2C0&istype=0&ie=utf-8&oe=utf-8&in=&cl=2&lm=-1&st=-1&cs=2202721532%2C3099894817&os=1973914981%2C428613933&simid=4092530312%2C469771017&adpicid=0&lpn=0&ln=1976&fr=&fmq=1489296515341_R&fm=rs6&ic=undefined&s=undefined&se=&sme=&tab=0&width=&height=&face=undefined&ist=&jit=&cg=&bdtype=0&oriquery=卡通圖片&objurl=http%3A%2F%2Fwww.demaxiya.com%2Fmoba%2Fattachment%2F1511%2F2-15111Q1042R26.jpg&fromurl=ippr_z2C%24qAzdH3FAzdH3Fooo_z%26e3B1j4wxtyw_z%26e3Bv54AzdH3F45kwAzdH3Foz6yAzdH3Ftg1jx88_z%26e3Bip4s&gsm=0&rpstart=0&rpnum=0"];
        NSData *imageData = [NSData dataWithContentsOfURL:url];
        
        UIImage *image = [UIImage imageWithData:imageData];
        
        NSLog(@"download----%@", [NSThread currentThread]);
        
        // 更新UI
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            self.imageView.image = image;
            NSLog(@"UI----%@", [NSThread currentThread]);
        }];
    }];
    
    [operationQueue addOperation:operation];
}

 download----<NSThread: 0x608000078440>{number = 5, name = (null)}
 UI----<NSThread: 0x60000006a100>{number = 1, name = main}

我們可以使用GCD隊(duì)列組下載兩種圖片合成一張圖片, Operation也能做到

- (void)viewDidLoad
{
    NSOperationQueue *operationQueue = [[NSOperationQueue alloc] init];
    
    __block UIImage *image1;
    __block UIImage *image2;
    NSBlockOperation *operationA = [NSBlockOperation blockOperationWithBlock:^{
        
        NSURL *url = [NSURL URLWithString:@"http://pic.qiantucdn.com/58pic/26/04/03/83S58PIC2Ev.jpg!qtwebp226"];
        NSData *imageData = [NSData dataWithContentsOfURL:url];
        
        image1 = [UIImage imageWithData:imageData];
        
        NSLog(@"downloadA----%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operationB = [NSBlockOperation blockOperationWithBlock:^{
        
        NSURL *url = [NSURL URLWithString:@"http://pic.qiantucdn.com/58pic/26/04/03/83S58PIC2Ev.jpg!qtwebp226"];
        NSData *imageData = [NSData dataWithContentsOfURL:url];
        
        image2 = [UIImage imageWithData:imageData];
        
        NSLog(@"downloadB----%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *combieOperation = [NSBlockOperation blockOperationWithBlock:^{
       
        UIGraphicsBeginImageContext(CGSizeMake(200, 200));
        
        [image1 drawInRect:CGRectMake(0, 0, 100, 200)];
        
        [image2 drawInRect:CGRectMake(100, 0, 100, 200)];
        
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        
        UIGraphicsEndImageContext();
        
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            
            self.imageView.image = image;
            
            NSLog(@"UI----%@", [NSThread currentThread]);
        }];
        
        
    }];

    
    [combieOperation addDependency:operationA];
    [combieOperation addDependency:operationB];

    
    [operationQueue addOperation:operationA];
    [operationQueue addOperation:operationB];
    [operationQueue addOperation:combieOperation];

    
}


 downloadB----<NSThread: 0x60000007e680>{number = 3, name = (null)}
 downloadA----<NSThread: 0x600000268100>{number = 4, name = (null)}
 UI----<NSThread: 0x608000076880>{number = 1, name = main}
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