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dispatch group使用方法详解

2024-11-23 20:34:39   203人阅读

第一、dispatch group可以用来将多个block组成一组以监测这些Block全部完成或者等待全部完成时发出的消息。使用函数dispatch_group_create来创建，然后使用函数dispatch_group_async来将block提交至一个dispatch queue，同时将它们添加至一个组。使用dispatch_group_notify,增加监听，当group内的block全部执行完时，再执行该函数指定的block

dispatch_queue_t queue=dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
    dispatch_group_t group=dispatch_group_create();
    dispatch_group_async(group, queue, ^{
        [NSThread sleepForTimeInterval:4];
        NSLog(@"blk0");});
    dispatch_group_async(group, queue, ^{
        [NSThread sleepForTimeInterval:2];
        NSLog(@"blk1");});
    dispatch_group_async(group, queue, ^{
        [NSThread sleepForTimeInterval:3];
        NSLog(@"blk2");});
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{NSLog(@"done");});

    NSLog(@"HELLO");


    执行结果：
2015-01-30 17:18:00.845 testApp[1870:60b] HELLO
2015-01-30 17:18:02.847 testApp[1870:3607] blk1
2015-01-30 17:18:03.848 testApp[1870:3807] blk2
2015-01-30 17:18:04.846 testApp[1870:1903] blk0
2015-01-30 17:18:04.849 testApp[1870:60b] done
第二、dispatch_group_wait(group, DISPATCH_TIME_FOREVER); 
等待group关联的block执行完毕，也可以设置超时参数，如果dispatch_group_wait函数的返回值不为零，说明group内处理为结束，否则为零
dispatch_queue_t queue=dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
    dispatch_group_t group=dispatch_group_create();
    dispatch_group_async(group, queue, ^{
        [NSThread sleepForTimeInterval:4];
        NSLog(@"blk0");});
    dispatch_group_async(group, queue, ^{
        [NSThread sleepForTimeInterval:2];
        NSLog(@"blk1");});
    dispatch_group_async(group, queue, ^{
        [NSThread sleepForTimeInterval:3];
        NSLog(@"blk2");});
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{NSLog(@"done");});
    int result=dispatch_group_wait(group, dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC));
    if (result==0) {
        NSLog(@"the group has finished");
    }else{
        NSLog(@"the group is processing");
    }
    NSLog(@"hello");









dispatch group使用方法详解


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