iOS 倒计时的一种实现

1、view

[self performselectorinbackground:@selector(thread) withobject:nil];

- (void)thread
{
    for(int i=300;i>=0;i--)
    {
        _count = i;
        // 回调主线程
        [self performselectoronmainthread:@selector(mainthread) withobject:nil waituntildone:yes];
        sleep(1);
    }
}

// 此函数主线程执行
- (void)mainthread
{
    self.time.text=[nsstring stringwithformat:@"%d",_count];
    if (_count==0) {
        
    }
}