- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    //手動設置任務之間依賴關系，進而改變自動的執(zhí)行順序
    [self createDependency];
}

- (void)createDependency {
    /*需求：往非主隊列中添加三個任務Task1;Task2;Task3
      自動執(zhí)行順序：三個任務同時執(zhí)行
      改后的執(zhí)行順序:任務三等待任務一和任務二執(zhí)行完畢，才執(zhí)行
      依賴關系：task3->task2; task3->task1
     */
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    NSBlockOperation *firstOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"開始下載圖片一...");
        [NSThread sleepForTimeInterval:3];
        NSLog(@"下載圖片一完成");
    }];
    NSBlockOperation *secondOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"開始下載圖片二...");
        [NSThread sleepForTimeInterval:5];
        NSLog(@"下載圖片二完成");
    }];
    NSBlockOperation *thirdOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下載圖片三");
    }];
    //設置/添加依賴關系
    /* 注意點：
       1. 千萬不要造成循環(huán)依賴(死鎖)
       2. 依賴關系在添加到隊列之前
     */
    [thirdOperation addDependency:firstOperation];
    [thirdOperation addDependency:secondOperation];
    [queue addOperation:firstOperation];
    [queue addOperation:secondOperation];
    [queue addOperation:thirdOperation];
}

//同步執(zhí)行
- (IBAction)blockSync:(id)sender {
    //1.創(chuàng)建操作對象
    NSBlockOperation *operation = [[NSBlockOperation alloc] init];
    //2.添加任務
    [operation addExecutionBlock:^{
        //要執(zhí)行的任務
        NSLog(@"下載圖片一:%@", [NSThread currentThread]);
    }];
    [operation addExecutionBlock:^{
        //要執(zhí)行的任務
        NSLog(@"下載圖片二:%@", [NSThread currentThread]);
    }];
    [operation addExecutionBlock:^{
        //要執(zhí)行的任務
        NSLog(@"下載圖片三:%@", [NSThread currentThread]);
    }];
    [operation addExecutionBlock:^{
        //要執(zhí)行的任務
        NSLog(@"下載圖片四:%@", [NSThread currentThread]);
    }];
    [operation addExecutionBlock:^{
        //要執(zhí)行的任務
        NSLog(@"下載圖片五:%@", [NSThread currentThread]);
    }];
    //3.執(zhí)行任務(同步執(zhí)行任務幾乎不用；沒有規(guī)律)
    [operation start];
}
//異步執(zhí)行 -》保證子線程執(zhí)行
- (IBAction)blockAsync:(id)sender {
    //1.創(chuàng)建操作對象(方式二:常用; 創(chuàng)建和添加任務合二為一)
    NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下載圖片一:%@", [NSThread currentThread]);
    }];
    NSBlockOperation *anotherOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下載圖片二:%@", [NSThread currentThread]);
        //回到主線程(獲取主隊列)
//        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
//            //主線程執(zhí)行
//            NSLog(@"回到主線程更新界面:%@", [NSThread currentThread]);
//        }];
    }];
    
    NSBlockOperation *thirdOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下載圖片三....%@",[NSThread currentThread]);
    }];
    NSBlockOperation *forthOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下載圖片四....%@", [NSThread currentThread]);
    }];
    NSBlockOperation *fifthOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下載圖片五....%@", [NSThread currentThread]);
    }];
    NSBlockOperation *sixthOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"下載圖片六....%@", [NSThread currentThread]);
    }];
    
    //2.創(chuàng)建非主隊列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    //2.1 設置最大同時執(zhí)行的任務的個數(shù)
    queue.maxConcurrentOperationCount = 2;
    //3.操作對象放到非主隊列中(自動執(zhí)行)
    [queue addOperation:operation];
    [queue addOperation:anotherOperation];
    [queue addOperation:thirdOperation];
    [queue addOperation:forthOperation];
    [queue addOperation:fifthOperation];
    [queue addOperation:sixthOperation];
    
//    //如何暫停隊列中的所有任務；
//    [queue setSuspended:YES];
//    //把隊列中的所有暫停的任務重新啟動
//    [queue setSuspended:NO];
//    //如何取消隊列中的所有任務(不會恢復丈探；從隊列中移除)
//    [queue cancelAllOperations];
}