AddingBorder.swift

extension UIView {
    enum BorderSide {
        case left
        case right
        case top
        case bottom
    }
    
    func addBorder(toSide side: BorderSide, withColor color: UIColor, withThickness thickness: CGFloat) {
        let border = CALayer()
        border.backgroundColor = color.cgColor
        
        switch side {
        case .left:
            border.frame = CGRect(x: frame.minX, y: frame.minY, width: thickness, height: frame.size.height)
        case .right:
            border.frame = CGRect(x: frame.maxX, y: frame.minY, width: thickness, height: frame.size.height)
        case .top:
            border.frame = CGRect(x: frame.minX, y: frame.minY, width: frame.size.width, height: thickness)
        case .bottom:
            border.frame = CGRect(x: frame.minX, y: frame.maxY, width: frame.size.width, height: thickness)
        }
    }
}