代码块只执行一次

(1)创建单例

+ (instancetype)cacher {

    static MHPCacher*cacher =nil;

    static dispatch_once_tonceToken;

    dispatch_once(&onceToken, ^{

        cacher = [MHPCachernew];

    });

    returncacher;

}

(2)防止重复执行代码块，如点击事件

static dispatch_once_t disOnce;

dispatch_once(&disOnce,^ {

    if([_delegate respondsToSelector:@selector(rewardDetailHeaderBtnTouchDelegateSelector:)]) {            

    [_delegate rewardDetailHeaderBtnTouchDelegateSelector:1001];

    }

});

延时

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.7* NSEC_PER_SEC)), dispatch_get_main_queue(), ^{

    CHPChildController vc =self.childViewControllers[self.selectedButton.tag-1];

    vc.loadPage =1;

    [vc requestListData];

});

网络请求队列

            dispatch_group_tgroup =dispatch_group_create();

            dispatch_queue_t q = dispatch_get_global_queue(0, 0);

            dispatch_group_enter(group);

            for(NSMutableDictionary*parameDicinpostArray) {

                dispatch_group_async(group, q, ^{

                    [AFHttp requestWihtMethod:MyRequestMethodTypePost url:@"api/Objects/newPraise" params:parameDic success:^(id response) {

                        NSLog(@"执行完成%@", parameDic);

                        //删除对应的数据

                        NSString*oidStr = [NSStringstringWithFormat:@"%@",parameDic[@"oId"]];

                        [[MHPCachercacher]clearCacheWith:PraiseTypeAndid:oidStr];

                    }failure:^(NSError*err) {

                    }];

                });

            }

            dispatch_group_notify(group, dispatch_get_main_queue(), ^{

                NSLog(@"所有队列完毕 %@", [NSThreadcurrentThread]);

                dispatch_group_leave(group);

            });

异步加载图片回到主线程刷新UI

__weak __typeof (self)weakSelf = self; dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

       NSURL *url = [NSURL URLWithString:adModel.sharePic];        

        weakSelf.shareImage = [UIImage imageWithData:[NSData dataWithContentsOfURL:url]];

        dispatch_async(dispatch_get_main_queue(), ^{

        self.shareImageView.image = weakSelf.shareImage;

});

});

创建定时器

-(void)gcdTimer{

    //定义队列

//声明

@property (nonatomic, strong) dispatch_source_t timer;

//创建

-(void)createGCDTimer{

    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);

    //创建定时器

    self.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,0,0, queue);

    dispatch_time_tstart =DISPATCH_TIME_NOW;        //当前时间

    dispatch_time_tinterval =1.0*NSEC_PER_SEC;    //间隔时间  --秒

    //设置定时器

    dispatch_source_set_timer(self.timer, start, interval,0);

    //设置回调

    dispatch_source_set_event_handler(self.timer, ^{

        NSLog(@"-------%@",[NSThread currentThread]);

        [selfcountDownTimerSelector];

    });

}

//使用

            dispatch_resume(self.timer);