// 创建队列
NSOperationQueue *queue = [[NSOperationQueue alloc] init];

// 创建操作
NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
// operation直接调用start，是同步执行（在当前线程执行操作）
// [operation start];

// 添加操作到队列中，会自动异步执行
[queue addOperation:operation];

NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"1- %@", [NSThread currentThread]);
    }];
[op1 start];

@implementation XMGOperation

- (void)main
{
    NSLog(@"%s, %@", __func__,[NSThread currentThread]);
}
@end

    // 1.创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    // 2.封装任务
    NSInvocationOperation *op1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(demo) object:nil];
    // 3.将任务添加到队列中
    [queue addOperation:op1];

    // 1.创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    // 2.封装任务
     NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{
     NSLog(@"1 = %@", [NSThread currentThread]);
     }];
     // 3.将任务添加到队列中
     [queue addOperation:op1];

    // 1.创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];

    // addOperationWithBlock方法会做两件事情
    // 1.根据传入的block, 创建一个NSBlockOperation对象
    // 2.将内部创建好的NSBlockOperation对象, 添加到队列中

    // 2.将任务添加到队列中
    [queue addOperationWithBlock:^{
        NSLog(@"1 = %@", [NSThread currentThread]);
    }];
    [queue addOperationWithBlock:^{
        NSLog(@"2 = %@", [NSThread currentThread]);
    }];

    // 1.创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    // 2.封装任务
    XMGOperation *op1 = [[XMGOperation alloc] init];

    // 3.将任务添加到队列中
    [queue addOperation:op1];

// 如果是YES, 代表需要暂停
// 如果是NO ,代表恢复执行
self.queue.suspended = YES;

// 内部会调用所有任务的cancel方法
[self.queue cancelAllOperations];

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
// 开启子线程
[queue addOperationWithBlock:^{
        // 回到主线程
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
        }];

}];

    op1.completionBlock = ^{
        NSLog(@"第一张图片下载完毕");
    };
    op2.completionBlock = ^{
        NSLog(@"第二张图片下载完毕");
    };

---perform...
[self performSelectorOnMainThread:(SEL) withObject:(id) waitUnitlDone:(BOOL)];

---GCD
dispatch_async(dispatch_get_main_queue(),^{

});

---NSOperationQueue
[NSOperationQueue mainQueue] addOperationWithBlock:^{

}];