通过创建UIView的分类来实现,这样处理的前提是视图的frame已经固定，如果是使用了约束，可以重写drawrect方法，并在此设置圆角

.h文件如下

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface UIView (CusCorner)

/**
 设置指定位置的圆角

 @param rectCorner 圆角位置(该变量可使用或运算，用于同时设置多个圆角)
 @param radius 圆角半径
 @param borderWidth 边框宽度
 @param borderColor 边框颜色
 @param fillColor 填充色
 @param name 给子layer命名,防止重复设置增加开销
 */
- (void)setupRoundedCorners:(UIRectCorner)rectCorner
               cornerRadius:(CGFloat)radius
                borderWidth:(CGFloat)borderWidth
                borderColor:( UIColor * _Nullable )borderColor
                  fillColor:(UIColor * _Nullable)fillColor
                  layerName:(NSString * _Nullable)name;
@end

NS_ASSUME_NONNULL_END

.m文件如下

#import "UIView+CusCorner.h"

@implementation UIView (CusCorner)
- (void)setupRoundedCorners:(UIRectCorner)rectCorner
               cornerRadius:(CGFloat)radius
                borderWidth:(CGFloat)borderWidth
                borderColor:( UIColor * _Nullable )borderColor
                  fillColor:(UIColor * _Nullable)fillColor
                  layerName:(NSString * _Nullable)name{
//设置遮罩
    CAShapeLayer *mask=nil;
    if ([self.layer.mask.name isEqualToString:name]) {
        mask = self.layer.mask;
    } else {
        mask=[CAShapeLayer layer];
        mask.name = name;
    }
    UIBezierPath * path= [UIBezierPath bezierPathWithRoundedRect:self.bounds byRoundingCorners:rectCorner cornerRadii:CGSizeMake(radius,radius)];
    mask.path=path.CGPath;
    mask.frame=self.bounds;
    self.layer.mask = mask;
//设置边框及填充色
    __block CAShapeLayer *borderLayer = nil;
    if (name.length) {
        NSArray<CALayer *> *subLayers = self.layer.sublayers;
        [subLayers enumerateObjectsUsingBlock:^(CALayer * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
            if([obj.name isEqualToString:name]){
                borderLayer = (CAShapeLayer *)obj;
                *stop = YES;
            }
        }];
    }
    
    if (!borderLayer) {
        borderLayer=[CAShapeLayer layer];
        borderLayer.name = name;
        [self.layer addSublayer:borderLayer];
    }
    
    borderLayer.path=path.CGPath;
    if (fillColor) {
        borderLayer.fillColor = fillColor.CGColor;
    }
    if (borderColor) {
        borderLayer.strokeColor = borderColor.CGColor;
    }
    
    if (borderWidth > 0) {
        borderLayer.lineWidth = borderWidth;
    }
    borderLayer.frame = self.bounds;
}
@end

调用如下

//swift
cusView.setupRoundedCorners([.topLeft , .topRight , .bottomLeft],
                                cornerRadius: 12,
                                  borderWidth: 0, 
                                   borderColor: nil, 
                                                   fill:UIColor.clear, 
                                      layerName: "local")
//oc
[self.cusView setupRoundedCorners:UIRectCornerTopLeft|UIRectCornerTopRight 
                                     cornerRadius:15 
                                       borderWidth:0 
                                        borderColor:nil 
                                               fillColor:UIColor.clearColor 
                                          layerName:@"layername"];