Corner Borders for UIView

UIView+Borders.swift

//  MARK: Borders
public extension UIView {
	/**
	Adds borders to the given corners.
	- Parameter corners:	The corners to which borders should be added.
	- Parameter color:		The color of the borders.
	- Parameter length:		The length of each border across the view.
	- Parameter width:		The thickness of the borders.
	 */
	func addBorders(to corners: Set<Corner>, color: UIColor = .black, length: CGFloat = 16.0, width: CGFloat = 1.0) {
		guard !corners.isEmpty else { return }
		
		func createBorder() -> UIView {
			let borderView = UIView(frame: CGRect.zero)
			borderView.translatesAutoresizingMaskIntoConstraints = false
			borderView.backgroundColor = color
			return borderView
		}
		
		for corner in corners {
			switch corner {
			case .topLeading:
				let topBorder = createBorder()
				let leftBorder = createBorder()
				addSubview(topBorder)
				addSubview(leftBorder)
				NSLayoutConstraint.activate([
					topBorder.topAnchor.constraint(equalTo: topAnchor, constant: -width / 2.0),
					topBorder.leadingAnchor.constraint(equalTo: leadingAnchor),
					topBorder.widthAnchor.constraint(equalToConstant: length),
					topBorder.heightAnchor.constraint(equalToConstant: width),
					leftBorder.topAnchor.constraint(equalTo: topAnchor, constant: -width / 2.0),
					leftBorder.leadingAnchor.constraint(equalTo: leadingAnchor, constant: -width / 2.0),
					leftBorder.widthAnchor.constraint(equalToConstant: width),
					leftBorder.heightAnchor.constraint(equalToConstant: length)
					])
			case .topTrailing:
				let topBorder = createBorder()
				let rightBorder = createBorder()
				addSubview(topBorder)
				addSubview(rightBorder)
				NSLayoutConstraint.activate([
					topBorder.topAnchor.constraint(equalTo: topAnchor, constant: -width / 2.0),
					topBorder.trailingAnchor.constraint(equalTo: trailingAnchor),
					topBorder.widthAnchor.constraint(equalToConstant: length),
					topBorder.heightAnchor.constraint(equalToConstant: width),
					rightBorder.topAnchor.constraint(equalTo: topAnchor, constant: -width / 2.0),
					rightBorder.trailingAnchor.constraint(equalTo: trailingAnchor, constant: width / 2.0),
					rightBorder.widthAnchor.constraint(equalToConstant: width),
					rightBorder.heightAnchor.constraint(equalToConstant: length)
					])
			case .bottomTrailing:
				let bottomBorder = createBorder()
				let rightBorder = createBorder()
				addSubview(bottomBorder)
				addSubview(rightBorder)
				NSLayoutConstraint.activate([
					bottomBorder.bottomAnchor.constraint(equalTo: bottomAnchor, constant: width / 2.0),
					bottomBorder.trailingAnchor.constraint(equalTo: trailingAnchor),
					bottomBorder.widthAnchor.constraint(equalToConstant: length),
					bottomBorder.heightAnchor.constraint(equalToConstant: width),
					rightBorder.bottomAnchor.constraint(equalTo: bottomAnchor, constant: width / 2.0),
					rightBorder.trailingAnchor.constraint(equalTo: trailingAnchor, constant: width / 2.0),
					rightBorder.widthAnchor.constraint(equalToConstant: width),
					rightBorder.heightAnchor.constraint(equalToConstant: length)
					])
			case .bottomLeading:
				let bottomBorder = createBorder()
				let leftBorder = createBorder()
				addSubview(bottomBorder)
				addSubview(leftBorder)
				NSLayoutConstraint.activate([
					bottomBorder.bottomAnchor.constraint(equalTo: bottomAnchor, constant: width / 2.0),
					bottomBorder.leadingAnchor.constraint(equalTo: leadingAnchor),
					bottomBorder.widthAnchor.constraint(equalToConstant: length),
					bottomBorder.heightAnchor.constraint(equalToConstant: width),
					leftBorder.bottomAnchor.constraint(equalTo: bottomAnchor, constant: width / 2.0),
					leftBorder.leadingAnchor.constraint(equalTo: leadingAnchor, constant: -width / 2.0),
					leftBorder.widthAnchor.constraint(equalToConstant: width),
					leftBorder.heightAnchor.constraint(equalToConstant: length)
					])
			}
		}
	}
	//  MARK: Corner
	enum Corner {
		case topLeading
		case topTrailing
		case bottomTrailing
		case bottomLeading
	}
}