如何在UIImageView上画圆而不在objective-c中添加层？

// CircleImageView.h

#import <UIKit/UIKit.h>

@interface CircleImageView : UIImageView

@property (nonatomic, strong) UIColor *borderColor;
@property (nonatomic, assign) CGFloat borderWidth;

@end

// CircleImageView.m

#import "CircleImageView.h"

@implementation CircleImageView

- (void)drawRect:(CGRect)rect {
    [super drawRect:rect];
    
    // 获取当前视图的上下文
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    // 设置边框颜色
    CGContextSetStrokeColorWithColor(context, self.borderColor.CGColor);
    
    // 设置边框宽度
    CGContextSetLineWidth(context, self.borderWidth);
    
    // 计算圆形的半径和中心点
    CGFloat radius = MIN(rect.size.width, rect.size.height) / 2;
    CGPoint center = CGPointMake(rect.size.width / 2, rect.size.height / 2);
    
    // 绘制圆形路径
    CGContextAddArc(context, center.x, center.y, radius, 0, M_PI * 2, 0);
    
    // 绘制边框
    CGContextDrawPath(context, kCGPathStroke);
}

@end