可取消的GCD 定时器

#import"ViewController.h"

NSInteger count=0;

@interfaceViewController ()

@property (nonatomic, strong)dispatch_source_t time;

@end

@implementationViewController

- (void)viewDidLoad {

[super viewDidLoad];

}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

//获得队列

dispatch_queue_t queue = dispatch_get_global_queue(0,0);//创建一个定时器

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

//设置开始时间

dispatch_time_t start = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0*NSEC_PER_SEC));

//设置时间间隔

uint64_t interval = (uint64_t)(2.0*NSEC_PER_SEC);

//设置定时器

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

//设置回调

dispatch_source_set_event_handler(self.time, ^{

NSLog(@"执行操作");

//设置当执行五次是取消定时器

count++;

if(count ==5){

dispatch_cancel(self.time);

}

});//由于定时器默认是暂停的所以我们启动一下//启动定时器dispatch_resume(self.time);

}

@end