iOS-写一个GCD定时器

项目中有个需求：需要每秒请求下服务器。用GCD写了个定时器：

声明一个timer

static dispatch_source_t _timer

    // GCD定时器
    NSTimeInterval period = 1.0; //设置时间间隔
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    dispatch_source_set_timer(_timer, dispatch_walltime(NULL, 0), period * NSEC_PER_SEC, 0); //每秒执行
    
    dispatch_source_set_event_handler(_timer, ^{
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"每秒执行");
        });
    });
    // 开启定时器
    dispatch_resume(_timer);

记得关闭定时器

dispatch_source_cancel(_timer);