GCD实现定时器

//dispatch source定时器
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_source_t source = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
dispatch_queue_t mainq = dispatch_get_main_queue();//主线程

if (source) {

dispatch_source_set_timer(source, dispatch_walltime(DISPATCH_TIME_NOW, 0), 2 * NSEC_PER_SEC, 0);

dispatch_source_set_event_handler(source, ^{

dispatch_async(mainq, ^{

[self testTimerOper];
});

});
}

dispatch_resume(source);

//用户执行操作
-(void)testTimerOper {

NSLog(@"测试timer执行");
}