GCD定时器

//
// ViewController.m
//  GCD 定时器
//
//

#import "ViewController.h"

NSInteger count = 0;

@interface ViewController ()
@property (nonatomic, strong)dispatch_source_t time;

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
}

-(void)touchesBegan:(NSSet<UITouch *> *)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, ^{

//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