concurrent|1|dispatch_queue_t

job:挖坑。

1、一个人挖一个坑要2hours.

2、我要挖两个坑。

 

从这里引出并行。

objc中有

dispatch object 来做多线程的事。

 

这样，又可以看看关于dispatch的那些事。

比如我要下载两个图片，就好像是上面的挖两个坑！

代码如下 ：

 

 

 

     dispatch_queue_t myQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_async(myQueue, ^{

        __block UIImage *img = nil;

        dispatch_async(myQueue, ^{

            NSLog(@"testing");

        });

        dispatch_sync(myQueue, ^{



                



            NSString *url_str = [[NSString alloc] initWithString:@"http://apod.nasa.gov/apod/image/9712/orionfull_jcc_big.jpg"];

            NSData *img_data = [self downloadWithUrl:url_str];

            img = [[UIImage alloc] initWithData:img_data];



            [url_str release];

        });

        dispatch_sync(dispatch_get_main_queue(), ^{

            UIImageView *img_view = [[UIImageView alloc] initWithImage:img];



            img_view.frame = CGRectMake(0, 0, 480, 200);

            [self.view_controller.view addSubview:img_view];

            

            [img_view release];

        });

    });

    

    dispatch_async(myQueue, ^{

        __block UIImage *img = nil;

        dispatch_sync(myQueue, ^{



             



            NSString *url_str = [[[NSString alloc] initWithString:@"http://www.dabaoku.net/fengjing/tk/tiankong/006f.jpg"] autorelease];

            NSData *img_data = [self downloadWithUrl:url_str];

            img = [[UIImage alloc] initWithData:img_data];

            

            [url_str release];



        });

        dispatch_sync(dispatch_get_main_queue(), ^{

            UIImageView *img_view = [[UIImageView alloc] initWithFrame:self.view_controller.view.bounds];

            [img_view setImage:img];

            img_view.frame = CGRectMake(100,200, 150, 150);

            [self.view_controller.view addSubview:img_view];

            [img_view release];

        });

    });

    dispatch_release(myQueue);

 

 注意到有个dispatch_get_main_queue就是通知主thread作出更新的。

 

上源代码

https://github.com/snowleung/ios_concurrent_demo