- (void)viewDidLoad
{
    [super viewDidLoad];
    
    NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"---下载图片----11---%@", [NSThread currentThread]);
    }];
    
    [operation1 addExecutionBlock:^{
        NSLog(@"---下载图片----12---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"---下载图片----2---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"---下载图片----3---%@", [NSThread currentThread]);
    }];
    
    NSBlockOperation *operation4 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"---下载图片----4---%@", [NSThread currentThread]);
    }];
    
    // 1.创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    
    // 主队列
//    NSOperationQueue *queue = [NSOperationQueue mainQueue];
    
    // 2.添加操作到队列中（自动异步执行）
    [queue addOperation:operation1];
    [queue addOperation:operation2];
    [queue addOperation:operation3];
    [queue addOperation:operation4];
}

IOS多线程