关于同步和异步（二）

#pragma mark- 同步 + 串行 ：不会开线程，串行执行
-(void)syncChuan{
    NSLog(@"----%@",[NSThread currentThread] );
    //1,获取并发队列，
    dispatch_queue_t queue = dispatch_get_main_queue();
    NSLog(@"start");
    //2,同步函数把任务添加到队列
    dispatch_sync(queue, ^{
        NSLog(@"download1---%@",[NSThread currentThread]);
    });
    dispatch_sync(queue, ^{
        NSLog(@"download2---%@",[NSThread currentThread]);
    });
    dispatch_sync(queue, ^{
        NSLog(@"download3---%@",[NSThread currentThread]);
    });
    NSLog(@"end");
}

Snip20170327_13.png

#pragma mark- 异步 + 串行 ：会开一条线程，串行执行
-(void)asyncChuan {
    NSLog(@"----%@",[NSThread currentThread] );
    //1,获取并发队列，
  dispatch_queue_t queue = dispatch_queue_create("fff", DISPATCH_QUEUE_SERIAL);
    NSLog(@"start");
    //2,异步函数把任务添加到队列
    dispatch_async(queue, ^{
        NSLog(@"download1---%@",[NSThread currentThread]);
    });
    dispatch_async(queue, ^{
        NSLog(@"download2---%@",[NSThread currentThread]);
    });
    dispatch_async(queue, ^{
        NSLog(@"download3---%@",[NSThread currentThread]);
    });
    NSLog(@"end");
}

Snip20170327_14.png