GCD的一些方法使用

作者: T_aa | 来源:发表于2017-03-08 21:27 被阅读59次

1.dispatch_barrier_async
2.dispatch_apply
3.dispatch_group_t
4.dispatch_semaphore_t

dispatch_barrier_async
dispatch_barrier_async 或者 dispatch_barrier_sync 要添加在自定义的queue中，他会等待这个queue队列中先于他之前的任务执行完成之后再执行。
阻塞他之后的闭包任务。


//并发的
    dispatch_queue_t queue = dispatch_queue_create("com.lanhai.kkkk", DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_async(queue, ^{
//        [NSThread sleepForTimeInterval:5];
        NSLog(@"队列任务kkkk——————1");
        
        NSURL * url = [NSURL URLWithString:@"http://avatar.csdn.net/2/C/D/1_totogo2010.jpg"];
        NSData * data = [[NSData alloc]initWithContentsOfURL:url];
        UIImage *image = [[UIImage alloc]initWithData:data];
        if (data != nil) {
            dispatch_async(dispatch_get_main_queue(), ^{
                
                NSLog(@"队列任务kkkk——————111");
                
            });
        }
    });
    
    dispatch_async(queue, ^{
        NSLog(@"队列任务kkkk——————2");
    });
    
    dispatch_barrier_async(queue, ^{
        
        NSLog(@"队列任务kkkk------阻塞的队列 barrier 要等其他队列执行完成之后 才能执行吗 ，也必须加载在自己定义的队列中");
        
        [NSThread sleepForTimeInterval:1];
        
    });
    
    
    
    
    dispatch_async(queue, ^{
        
        NSLog(@"队列任务kkkk——————3 会等待barrier执行完成之后再执行");
        [NSThread sleepForTimeInterval:1];
    });
    
    
    
    dispatch_barrier_async(queue, ^{
        
        NSLog(@"队列任务kkkk------测试多个");
        
        [NSThread sleepForTimeInterval:1];
        
    });
    
    
    dispatch_async(queue, ^{
        
        NSLog(@"队列任务kkkk——————4 会等待barrier执行完成之后再执行");
    });
    
    NSLog(@"=========================_+++========++++++");

输出

BangBangXing[4466:70300] +++++++++++++++++++++++===================
2017-03-08 10:53:31.305 BangBangXing[4466:70300] =========================_+++========++++++
2017-03-08 10:53:31.305 BangBangXing[4466:70370] 队列任务kkkk——————1
2017-03-08 10:53:31.305 BangBangXing[4466:70499] 队列任务kkkk——————2
2017-03-08 10:53:32.363 BangBangXing[4466:70370] 队列任务kkkk------阻塞的队列 barrier 要等其他队列执行完成之后 才能执行吗 ，也必须加载在自己定义的队列中
2017-03-08 10:53:32.363 BangBangXing[4466:70300] 队列任务kkkk——————111
2017-03-08 10:53:33.428 BangBangXing[4466:70370] 队列任务kkkk——————3 会等待barrier执行完成之后再执行
2017-03-08 10:53:34.493 BangBangXing[4466:70370] 队列任务kkkk------测试多个
2017-03-08 10:53:35.568 BangBangXing[4466:70370] 队列任务kkkk——————4 会等待barrier执行完成之后再执行

dispatch_apply往队列queue中重复添加任务，会阻塞后面的线程，等待他里面添加的任务执行成功之后再往下继续执行。

NSLog(@"============== begin ==============");
    
    //并发的
    dispatch_queue_t queue = dispatch_queue_create("com.lanhai.kkkk", DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_async(queue, ^{

        [NSThread sleepForTimeInterval:2];
        NSLog(@"队列任务kkkk——————1");
    });
    
    //重复执行 将闭包里面的任务添加到queue中 添加5个
    dispatch_apply(5, queue, ^(size_t i) {
        
        [NSThread sleepForTimeInterval:1];
        
        NSLog(@"队列任务apply添加的kkkk——————%zu",i);
        
    });
    
    dispatch_async(queue, ^{
        
        [NSThread sleepForTimeInterval:2];
        NSLog(@"队列任务kkkk——————2");
    });
    
    
    dispatch_async(queue, ^{
    
        NSLog(@"队列任务kkkk——————3");
    });
    
    NSLog(@"============== end ==============");

打印

2017-03-08 11:15:41.799 BangBangXing[5609:83837] ============== begin ==============
2017-03-08 11:15:42.801 BangBangXing[5609:83947] 队列任务apply添加的kkkk——————2
2017-03-08 11:15:42.801 BangBangXing[5609:84041] 队列任务apply添加的kkkk——————1
2017-03-08 11:15:42.801 BangBangXing[5609:83837] 队列任务apply添加的kkkk——————0
2017-03-08 11:15:42.801 BangBangXing[5609:83940] 队列任务apply添加的kkkk——————3
2017-03-08 11:15:43.870 BangBangXing[5609:84018] 队列任务kkkk——————1
2017-03-08 11:15:43.870 BangBangXing[5609:83947] 队列任务apply添加的kkkk——————4
2017-03-08 11:15:43.871 BangBangXing[5609:83837] ============== end ==============
2017-03-08 11:15:43.871 BangBangXing[5609:84018] 队列任务kkkk——————3
2017-03-08 11:15:45.926 BangBangXing[5609:83947] 队列任务kkkk——————2

dispatch_group_t用来监视多个异步任务执行情况，一种是利用dispatch_wait来阻塞当前的进程，等待执行完成或者超时之后继续下一步执行。一种是利用dispatch_group_notify来监听所有任务执行完成之后的回调，不会阻塞，或者和enter和leave配合。

dispatch_group_wait

NSLog(@"============== begin ==============");
    
    dispatch_queue_t queue = dispatch_queue_create("com.lanhai.group", DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_group_t group = dispatch_group_create();
    
    dispatch_group_async(group, queue, ^{
        NSLog(@"执行任务1");
    });
    
    dispatch_group_async(group, queue, ^{
        
        [NSThread sleepForTimeInterval:5];
        NSLog(@"执行任务2");
    });
    
    dispatch_group_async(group, queue, ^{
        
        [NSThread sleepForTimeInterval:5];
        NSLog(@"执行任务3");
    });
    
    dispatch_group_async(group, queue, ^{
        NSLog(@"执行任务4");
    });
    
    //设置超时时间
    dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
    
    
    NSLog(@"============== end ==============");

打印

2017-03-08 11:36:57.511 BangBangXing[6987:96675] ============== begin ==============
2017-03-08 11:36:57.512 BangBangXing[6987:96761] 执行任务1
2017-03-08 11:36:57.512 BangBangXing[6987:96839] 执行任务4
2017-03-08 11:37:02.583 BangBangXing[6987:96767] 执行任务3
2017-03-08 11:37:02.583 BangBangXing[6987:96768] 执行任务2
2017-03-08 11:37:02.584 BangBangXing[6987:96675] ============== end ==============

dispatch_group_notify

NSLog(@"============== begin ==============");
    
    dispatch_queue_t queue = dispatch_queue_create("com.lanhai.group", DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_group_t group = dispatch_group_create();
    
    dispatch_group_async(group, queue, ^{
        NSLog(@"执行任务1");
    });
    
    dispatch_group_async(group, queue, ^{
        
        [NSThread sleepForTimeInterval:5];
        NSLog(@"执行任务2");
    });
    
    dispatch_group_async(group, queue, ^{
        
        [NSThread sleepForTimeInterval:5];
        NSLog(@"执行任务3");
    });
    
    dispatch_group_async(group, queue, ^{
        NSLog(@"执行任务4");
    });
    
    dispatch_group_notify(group, queue, ^{
        NSLog(@"所有任务执行完成");
    });
    
    
    NSLog(@"============== end ==============");

打印

2017-03-08 11:48:24.310 BangBangXing[7362:101941] ============== begin ==============
2017-03-08 11:48:24.312 BangBangXing[7362:101941] ============== end ==============
2017-03-08 11:48:24.312 BangBangXing[7362:102007] 执行任务1
2017-03-08 11:48:24.312 BangBangXing[7362:102000] 执行任务4
2017-03-08 11:48:29.359 BangBangXing[7362:102095] 执行任务2
2017-03-08 11:48:29.359 BangBangXing[7362:102009] 执行任务3
2017-03-08 11:48:29.359 BangBangXing[7362:102009] 所有任务执行完成

dispatch_group_enter 和 dispatch_group_leave

enter和leave是成对出现的，开始一个任务之前要先enter 任务完成之后再leave，他们相当于一个dispatch_group_async执行

NSLog(@"============== begin ==============");
    
    dispatch_queue_t queue = dispatch_queue_create("com.lanhai.group", DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_group_t group = dispatch_group_create();
    
    dispatch_group_enter(group);
    [YHHttps httpsGetWithURL:@"http://www.weather.com.cn/data/sk/101010100.html" andParameterDic:nil andResponseBlock:^(RequestResultObj *resultObj) {
        
        NSLog(@"请求任务1完成");
        dispatch_group_leave(group);
    }];
    
    dispatch_group_enter(group);
    [YHHttps httpsGetWithURL:@"http://baike.baidu.com/api/openapi/BaikeLemmaCardApi?scope=103&format=json&appid=379020&bk_key=%E9%93%B6%E9%AD%82&bk_length=600" andParameterDic:nil andResponseBlock:^(RequestResultObj *resultObj) {
        
        NSLog(@"请求任务2完成");
        dispatch_group_leave(group);
    }];
    
    dispatch_group_notify(group, queue, ^{
        NSLog(@"所有任务执行完成");
    });
    
    
    NSLog(@"============== end ==============");

输出

2017-03-08 12:45:56.875 BangBangXing[7999:120101] ============== begin ==============
2017-03-08 12:45:56.882 BangBangXing[7999:120101] ============== end ==============
2017-03-08 12:45:57.080 BangBangXing[7999:120101] 请求任务2完成
2017-03-08 12:45:57.082 BangBangXing[7999:120101] 请求任务1完成
2017-03-08 12:45:57.082 BangBangXing[7999:120338] 所有任务执行完成

dispatch_semaphore_t信号量。
singal 信号量+1，释放资源了+1
wait 信号量-1，要占用资源了-1
信号量总数大于等于0的时候程序继续执行，
信号量总数小于0的时候阻塞等待

NSLog(@"============== begin ==============");
    
    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
    
    dispatch_queue_t queue = dispatch_queue_create("com.lanhai.semaphore", DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_async(queue, ^{
        
        [NSThread sleepForTimeInterval:3];
        
        NSLog(@"semaphore + 1");
        
        dispatch_semaphore_signal(semaphore);
        
    });
    
    NSLog(@"semaphore - 1");
    
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    
    NSLog(@"============== end ==============");

输出

2017-03-08 14:07:46.797 BangBangXing[8815:146733] ============== begin ==============
2017-03-08 14:07:46.797 BangBangXing[8815:146733] semaphore - 1
2017-03-08 14:07:49.798 BangBangXing[8815:146830] semaphore + 1
2017-03-08 14:07:49.798 BangBangXing[8815:146733] ============== end ==============

GCD的一些方法使用

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