UIView设置边框(整体设置和分开设置)

在开发中为UIView设置边框是常常用到的功能，如果要为UIView四下都设置边框，最简单的方法是使用CALayer的border属性：

+(void)setViewBorder:(UIView *)view color:(UIColor *)color radius:(float)radius border:(float)border{
    //设置layer
    CALayer *layer=[view layer];
    //是否设置边框以及是否可见
    [layer setMasksToBounds:YES];
    //设置边框圆角的弧度
    [layer setCornerRadius:radius];
    //设置边框线的宽
    [layer setBorderWidth:border];
    //设置边框线的颜色
    [layer setBorderColor:[color CGColor]];
}

但是在实际中往往需要灵活的设置某几条或者某一条边框，那么该怎么做呢？下面就是提供的方法：

typedef NS_ENUM(NSInteger, UIViewBorderLineType) {
    UIViewBorderLineTypeTop,
    UIViewBorderLineTypeRight,
    UIViewBorderLineTypeBottom,
    UIViewBorderLineTypeLeft,
};

+(void)setViewBorder:(UIView *)view color:(UIColor *)color border:(float)border type:(UIViewBorderLineType)borderLineType{
    CALayer *lineLayer = [CALayer layer];
    lineLayer.backgroundColor = color.CGColor;
    switch (borderLineType) {
        case UIViewBorderLineTypeTop:{
            lineLayer.frame = CGRectMake(0, 0, view.frame.size.width, border);
            break;
        }
        case UIViewBorderLineTypeRight:{
            lineLayer.frame = CGRectMake(view.frame.size.width, 0, border, view.frame.size.height);
            break;
        }
        case UIViewBorderLineTypeBottom:{
            lineLayer.frame = CGRectMake(0, view.frame.size.height, view.frame.size.width,border);
            break;
        }
        case UIViewBorderLineTypeLeft:{
            lineLayer.frame = CGRectMake(0, 0, border, view.frame.size.height);
            break;
        }
            
        default:{
            lineLayer.frame = CGRectMake(0, 0, view.frame.size.width-42, border);
            break;
        }
    }
    
    [view.layer addSublayer:lineLayer];
}

本质上也是实用UIView的layer，然后为其添加子layer。