略微封装了一下，给View添加指定位置的边框线，其中位移枚举的使用询问了哥们儿，总算搞定；
封装一：直接封装成了一个方法

/// 边框类型(位移枚举)
typedef NS_ENUM(NSInteger, UIBorderSideType) {
    UIBorderSideTypeAll    = 0,
    UIBorderSideTypeTop    = 1 << 0,
    UIBorderSideTypeBottom = 1 << 1,
    UIBorderSideTypeLeft   = 1 << 2,
    UIBorderSideTypeRight  = 1 << 3,
};

/**
 设置view指定位置的边框

 @param originalView   原view
 @param color          边框颜色
 @param borderWidth    边框宽度
 @param borderType     边框类型 例子: UIBorderSideTypeTop|UIBorderSideTypeBottom
 @return  view
 */
- (UIView *)borderForView:(UIView *)originalView color:(UIColor *)color borderWidth:(CGFloat)borderWidth borderType:(UIBorderSideType)borderType {
    
    if (borderType == UIBorderSideTypeAll) {
        originalView.layer.borderWidth = borderWidth;
        originalView.layer.borderColor = color.CGColor;
        return originalView;
    }
    
    /// 线的路径
    UIBezierPath * bezierPath = [UIBezierPath bezierPath];
    
    /// 左侧
    if (borderType & UIBorderSideTypeLeft) {
        /// 左侧线路径
        [bezierPath moveToPoint:CGPointMake(0.0f, originalView.frame.size.height)];
        [bezierPath addLineToPoint:CGPointMake(0.0f, 0.0f)];
    }
    
    /// 右侧
    if (borderType & UIBorderSideTypeRight) {
        /// 右侧线路径
        [bezierPath moveToPoint:CGPointMake(originalView.frame.size.width, 0.0f)];
        [bezierPath addLineToPoint:CGPointMake( originalView.frame.size.width, originalView.frame.size.height)];
    }
    
    /// top
    if (borderType & UIBorderSideTypeTop) {
        /// top线路径
        [bezierPath moveToPoint:CGPointMake(0.0f, 0.0f)];
        [bezierPath addLineToPoint:CGPointMake(originalView.frame.size.width, 0.0f)];
    }
    
    /// bottom
    if (borderType & UIBorderSideTypeBottom) {
        /// bottom线路径
        [bezierPath moveToPoint:CGPointMake(0.0f, originalView.frame.size.height)];
        [bezierPath addLineToPoint:CGPointMake( originalView.frame.size.width, originalView.frame.size.height)];
    }
  
    CAShapeLayer * shapeLayer = [CAShapeLayer layer];
    shapeLayer.strokeColor = color.CGColor;
    shapeLayer.fillColor  = [UIColor clearColor].CGColor;
    /// 添加路径
    shapeLayer.path = bezierPath.CGPath;
    /// 线宽度
    shapeLayer.lineWidth = borderWidth;
    
    [originalView.layer addSublayer:shapeLayer];
    
    return originalView;
}

封装二：封装成了类别

/// .h内容
#import <UIKit/UIKit.h>

typedef NS_OPTIONS(NSUInteger, UIBorderSideType) {
    UIBorderSideTypeAll  = 0,
    UIBorderSideTypeTop = 1 << 0,
    UIBorderSideTypeBottom = 1 << 1,
    UIBorderSideTypeLeft = 1 << 2,
    UIBorderSideTypeRight = 1 << 3,
};

@interface UIView (BorderLine)

- (UIView *)borderForColor:(UIColor *)color borderWidth:(CGFloat)borderWidth borderType:(UIBorderSideType)borderType;

@end

/// .m内容

#import "UIView+BorderLine.h"

@implementation UIView (BorderLine)

- (UIView *)borderForColor:(UIColor *)color borderWidth:(CGFloat)borderWidth borderType:(UIBorderSideType)borderType {
    
    if (borderType == UIBorderSideTypeAll) {
        self.layer.borderWidth = borderWidth;
        self.layer.borderColor = color.CGColor;
        return self;
    }
    
    
    /// 左侧
    if (borderType & UIBorderSideTypeLeft) {
        /// 左侧线路径
        [self.layer addSublayer:[self addLineOriginPoint:CGPointMake(0.f, 0.f) toPoint:CGPointMake(0.0f, self.frame.size.height) color:color borderWidth:borderWidth]];
    }
    
    /// 右侧
    if (borderType & UIBorderSideTypeRight) {
        /// 右侧线路径
        [self.layer addSublayer:[self addLineOriginPoint:CGPointMake(self.frame.size.width, 0.0f) toPoint:CGPointMake( self.frame.size.width, self.frame.size.height) color:color borderWidth:borderWidth]];
    }
    
    /// top
    if (borderType & UIBorderSideTypeTop) {
        /// top线路径
        [self.layer addSublayer:[self addLineOriginPoint:CGPointMake(0.0f, 0.0f) toPoint:CGPointMake(self.frame.size.width, 0.0f) color:color borderWidth:borderWidth]];
    }
    
    /// bottom
    if (borderType & UIBorderSideTypeBottom) {
        /// bottom线路径
        [self.layer addSublayer:[self addLineOriginPoint:CGPointMake(0.0f, self.frame.size.height) toPoint:CGPointMake( self.frame.size.width, self.frame.size.height) color:color borderWidth:borderWidth]];
    }
    
    return self;
}

- (CAShapeLayer *)addLineOriginPoint:(CGPoint)p0 toPoint:(CGPoint)p1 color:(UIColor *)color borderWidth:(CGFloat)borderWidth {

    /// 线的路径
    UIBezierPath * bezierPath = [UIBezierPath bezierPath];
    [bezierPath moveToPoint:p0];
    [bezierPath addLineToPoint:p1];
    
    CAShapeLayer * shapeLayer = [CAShapeLayer layer];
    shapeLayer.strokeColor = color.CGColor;
    shapeLayer.fillColor  = [UIColor clearColor].CGColor;
    /// 添加路径
    shapeLayer.path = bezierPath.CGPath;
    /// 线宽度
    shapeLayer.lineWidth = borderWidth;
    return shapeLayer;
}

@end

用法：

UIView *testView = [[UIView alloc] initWithFrame:CGRectMake(80.0f, 80.0f, 200.0f, 100.0f)];
    testView.backgroundColor = [UIColor lightGrayColor];
    [self.view addSubview:testView];
    [self borderForView:testView color:[UIColor redColor] borderWidth:1.0f borderType:UIBorderSideTypeLeft | UIBorderSideTypeTop | UIBorderSideTypeBottom];

效果：

C1846502-36A3-4BD0-A118-D808444D09A0.png

不足之处：
边框线过宽的话，交界处会有留白；

PS:第一次用简书发文章，常用CSDN，我的CSDN看看相关iOS开发文章，都是平时我遇到的问题，解决了，记录下来，CSDN地址：http://blog.csdn.net/syg90178aw

注意，需要先把你的view加载在父view上，[self.view addSubview:testView]; 之后再设置边框；否则可能会不起作用的；