如果想着做一个类似的家里的圆形时钟的样式的钟表，可以使用这样的方法：

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic,weak)CALayer *second;

@property (nonatomic ,weak)CALayer *minute;

@property (nonatomic ,weak)CALayer *hour;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    self.view.backgroundColor = [UIColor cyanColor];

    //创建表盘

    CALayer *clock = [[CALayer alloc]init];

    //大小

    clock.bounds = CGRectMake(0, 0, 200, 200);

    //位置

    clock.position = CGPointMake(200, 200);

    //内容

    clock.contents = (__bridge id _Nullable)([UIImage imageNamed:@"clock"].CGImage);

    [self.view.layer addSublayer:clock];

    //圆角

    clock.cornerRadius = 100;

    //裁剪

    clock.masksToBounds = YES;

    

    //创建秒针

    CALayer *second = [[CALayer alloc]init];

    self.second = second;

    //大小

    second.bounds = CGRectMake(0, 0, 2, 100);

    //位置

    second.position = clock.position;

    //颜色

    second.backgroundColor = [UIColor redColor].CGColor;

    //锚点

    second.anchorPoint = CGPointMake(0.5, 0.8);

    [self.view.layer addSublayer:second];

    

    //创建分针

    CALayer *minute = [[CALayer alloc]init];

    self.minute = minute;

    //大小

    minute.bounds = CGRectMake(0, 0, 3, 80);

    //位置

    minute.position = clock.position;

    //颜色

    minute.backgroundColor = [UIColor blueColor].CGColor;

    //锚点

    minute.anchorPoint = CGPointMake(0.5, 0.8);

    [self.view.layer addSublayer:minute];

    

    //创建时针

    CALayer *hour = [[CALayer alloc]init];

    self.hour = hour;

    //大小

    hour.bounds = CGRectMake(0, 0, 4, 60);

    //位置

    hour.position = clock.position;

    //颜色

    hour.backgroundColor = [UIColor purpleColor].CGColor;

    //锚点

    hour.anchorPoint = CGPointMake(0.5, 0.8);

    [self.view.layer addSublayer:hour];

    

    CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(timeChange)];

    [link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];

    [self timeChange];

}

-(void)timeChange{

    NSDate *date = [NSDate date];

//

//    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];

//    formatter.dateFormat = @"ss";

//    NSString *ms = [formatter stringFromDate:date];

//    CGFloat msValue = [ms floatValue];

    NSCalendar *cal = [NSCalendar currentCalendar];

    CGFloat ms = [cal component:NSCalendarUnitNanosecond fromDate:date];

    CGFloat s= [cal component:NSCalendarUnitSecond fromDate:date];

    CGFloat m = [cal component:NSCalendarUnitMinute fromDate:date];

    CGFloat h = [cal component:NSCalendarUnitHour fromDate:date];

    

    //秒针角度

    CGFloat angle = (2 * M_PI/60) / 1000000000;

    CGFloat angle1 = 2 * M_PI / 60;

    self.second.affineTransform = CGAffineTransformMakeRotation(angle1 * s + angle * ms);

    //分针角度

    CGFloat minuteAngle = 2 * M_PI / 60;

    self.minute.affineTransform = CGAffineTransformMakeRotation(minuteAngle * m + angle1 * s / 60 + angle * ms / 60);

    //时针角度

    CGFloat hourAngle = 2 * M_PI / 12;

    self.hour.affineTransform = CGAffineTransformMakeRotation(hourAngle * h + minuteAngle * m / 12 + angle1 * s / 60 + angle * ms / 60);

    

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

@end

当然还要有一个这样的表盘，

其实代码实现主要是用的CALayer的一些动画效果实现的。