Labels edges of a given view

UIView+LabeledEdges.swift

extension UIView {
    struct LabeledEdge: OptionSet {
        let rawValue: Int

        static let leading = Self(rawValue: 1 << 0)
        static let top = Self(rawValue: 1 << 1)
        static let trailing = Self(rawValue: 1 << 2)
        static let bottom = Self(rawValue: 1 << 3)

        static let all: Self = [.leading, .top, .trailing, .bottom]
    }

    @discardableResult
    func labelEdges(_ edges: LabeledEdge, with text: String) -> [UILabel] {
        let setupLabel: (String) -> UILabel = { text in
            let label = UILabel()
            label.alpha = 0.5
            label.font = UIFont.systemFont(ofSize: 10)
            label.textColor = .label
            label.text = text
            label.translatesAutoresizingMaskIntoConstraints = false
            return label
        }

        var labelsToReturn: [UILabel] = []

        if edges.contains(.leading) {
            let label = setupLabel("\(text) (leading)")
            label.transform = CGAffineTransform(rotationAngle: -CGFloat.pi / 2)
            addSubview(label)

            label.centerXAnchor.constraint(equalTo: leadingAnchor, constant: label.font.lineHeight / 2).isActive = true
            label.centerYAnchor.constraint(equalTo: centerYAnchor).isActive = true

            labelsToReturn.append(label)
        }

        if edges.contains(.top) {
            let label = setupLabel("\(text) (top)")
            addSubview(label)

            label.centerXAnchor.constraint(equalTo: centerXAnchor).isActive = true
            label.centerYAnchor.constraint(equalTo: topAnchor, constant: label.font.lineHeight / 2).isActive = true

            labelsToReturn.append(label)
        }

        if edges.contains(.trailing) {
            let label = setupLabel("\(text) (trailing)")
            label.transform = CGAffineTransform(rotationAngle: CGFloat.pi / 2)
            addSubview(label)

            label.centerXAnchor.constraint(equalTo: trailingAnchor, constant: -label.font.lineHeight / 2).isActive = true
            label.centerYAnchor.constraint(equalTo: centerYAnchor).isActive = true

            labelsToReturn.append(label)
        }

        if edges.contains(.bottom) {
            let label = setupLabel("\(text) (bottom)")
            addSubview(label)

            label.centerYAnchor.constraint(equalTo: bottomAnchor, constant: -label.font.lineHeight / 2).isActive = true
            label.centerXAnchor.constraint(equalTo: centerXAnchor).isActive = true

            labelsToReturn.append(label)
        }

        return labelsToReturn
    }
}

Here are some examples of how it can be used:

Edges: .all	Edges: [.leading, .top]