Add border to UIView

addBorderToUIView.swift

extension UIView {
    func addBorder(edges: UIRectEdge, colour: UIColor = UIColor.white, thickness: CGFloat = 1) -> [UIView] {
        
        var borders = [UIView]()
        
        func border() -> UIView {
            let border = UIView(frame: CGRect.zero)
            border.backgroundColor = colour
            border.translatesAutoresizingMaskIntoConstraints = false
            return border
        }
        
        if edges.contains(.top) || edges.contains(.all) {
            let top = border()
            addSubview(top)
            addConstraints(
                NSLayoutConstraint.constraints(withVisualFormat: "V:|-(0)-[top(==thickness)]",
                                                               options: [],
                                                               metrics: ["thickness": thickness],
                                                               views: ["top": top]))
            addConstraints(
                NSLayoutConstraint.constraints(withVisualFormat: "H:|-(0)-[top]-(0)-|",
                                                               options: [],
                                                               metrics: nil,
                                                               views: ["top": top]))
            borders.append(top)
        }
        
        if edges.contains(.left) || edges.contains(.all) {
            let left = border()
            addSubview(left)
            addConstraints(
                NSLayoutConstraint.constraints(withVisualFormat: "H:|-(0)-[left(==thickness)]",
                                                               options: [],
                                                               metrics: ["thickness": thickness],
                                                               views: ["left": left]))
            addConstraints(
                NSLayoutConstraint.constraints(withVisualFormat: "V:|-(0)-[left]-(0)-|",
                                                               options: [],
                                                               metrics: nil,
                                                               views: ["left": left]))
            borders.append(left)
        }
        
        if edges.contains(.right) || edges.contains(.all) {
            let right = border()
            addSubview(right)
            addConstraints(
                NSLayoutConstraint.constraints(withVisualFormat: "H:[right(==thickness)]-(0)-|",
                                                               options: [],
                                                               metrics: ["thickness": thickness],
                                                               views: ["right": right]))
            addConstraints(
                NSLayoutConstraint.constraints(withVisualFormat: "V:|-(0)-[right]-(0)-|",
                                                               options: [],
                                                               metrics: nil,
                                                               views: ["right": right]))
            borders.append(right)
        }
        
        if edges.contains(.bottom) || edges.contains(.all) {
            let bottom = border()
            addSubview(bottom)
            addConstraints(
                NSLayoutConstraint.constraints(withVisualFormat: "V:[bottom(==thickness)]-(0)-|",
                                                               options: [],
                                                               metrics: ["thickness": thickness],
                                                               views: ["bottom": bottom]))
            addConstraints(
                NSLayoutConstraint.constraints(withVisualFormat: "H:|-(0)-[bottom]-(0)-|",
                                                               options: [],
                                                               metrics: nil,
                                                               views: ["bottom": bottom]))
            borders.append(bottom)
        }
        
        return borders
    }
}