How to add a border just on the top side of a UIView

Question

My question is on the title.

I don't know how to add a border in a specific side, top or bottom, any side... layer.border draws the border for the whole view...

Answer 1

I consider subclassing UIView and overriding drawRect overkill here. Why not add an extension on UIView and add border subviews?

@discardableResult func addBorders(edges: UIRectEdge,                 color: UIColor,                 inset: CGFloat = 0.0,                 thickness: CGFloat = 1.0) -> [UIView] {      var borders = [UIView]()      @discardableResult     func addBorder(formats: String...) -> UIView {         let border = UIView(frame: .zero)         border.backgroundColor = color         border.translatesAutoresizingMaskIntoConstraints = false         addSubview(border)         addConstraints(formats.flatMap {             NSLayoutConstraint.constraints(withVisualFormat: $0,                                            options: [],                                            metrics: ["inset": inset, "thickness": thickness],                                            views: ["border": border]) })         borders.append(border)         return border     }       if edges.contains(.top) || edges.contains(.all) {         addBorder(formats: "V:|-0-[border(==thickness)]", "H:|-inset-[border]-inset-|")     }      if edges.contains(.bottom) || edges.contains(.all) {         addBorder(formats: "V:[border(==thickness)]-0-|", "H:|-inset-[border]-inset-|")     }      if edges.contains(.left) || edges.contains(.all) {         addBorder(formats: "V:|-inset-[border]-inset-|", "H:|-0-[border(==thickness)]")     }      if edges.contains(.right) || edges.contains(.all) {         addBorder(formats: "V:|-inset-[border]-inset-|", "H:[border(==thickness)]-0-|")     }      return borders }      // Usage:              view.addBorder(edges: [.all]) // All with default arguments      view.addBorder(edges: [.top], color: .green) // Just Top, green, default thickness     view.addBorder(edges: [.left, .right, .bottom], color: .red, thickness: 3) // All except Top, red, thickness 3 

With this code you're not tied to your subclass too, you can apply it to anything and everything that inherits from UIView - reusable in your project, and any others. Pass in other arguments to your methods to define other colours and widths. Many options.