NSTime 定时器

• 创建NSTime

    // 创建一个定时器
    NSTime timer = [NSTimer scheduledTimerWithTimeInterval:1.5 target:self selector:@selector(nextPage) userInfo:nil repeats:YES];

    // 将定时器加入主运行循环
    [[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];

    // 将NSTime赋值给自己的成员变量
    self.time = time;

    // 将定时器停止
    [self.timer invalidate];

    // 将定时器暂停

    // 创建时钟对象
    self.time = [CADisplayLink displayLinkWithTarget:self selector:@selector(step)];

    // 将时钟添加到主运行循环
    [self.time addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];

    // 将定时器停止
    [self.timer invalidate];

    // 将定时器暂停
    self.time.paused = !self.time.paused;