Key-value view

Example.swift

enum Keys: String, CaseIterable {
    case nicknames = "Nicknames"
    case calendars = "Calendars"
    case born = "Born"
}

let kvView = KVView<Keys>()
kvView[.nicknames].value = event.aggregatedNicknamesDescription
kvView[.calendars].value = event.aggregatedCalendarsDescription
kvView[.born].value = formatter.string(from: birthdate)

KVView.swift

import UIKit

class KVRow<Key>: UIStackView where Key: CaseIterable, Key: RawRepresentable, Key.RawValue == String {
    
    let key: Key
    
    var value: String? {
        get {
            valueLabel.text
        }
        set {
            valueLabel.text = newValue
        }
    }

    private let keyLabel = UILabel()
    
    private let valueLabel = UILabel()
    
    private let valueStackView = UIStackView()
    
    private let drawDebug: Bool
    
    init(key: Key, drawDebug: Bool) {
        self.key = key
        self.drawDebug = drawDebug
        super.init(frame: .zero)
        axis = .horizontal
        
        keyLabel.font = UIFont.preferredFont(for: .subheadline, trait: nil, weight: .regular)
        keyLabel.textColor = .lightGray
        keyLabel.textAlignment = .left
        keyLabel.text = key.rawValue
        
        valueLabel.font = UIFont.preferredFont(for: .subheadline, trait: nil, weight: .regular)
        valueLabel.textColor = .darkText
        valueLabel.textAlignment = .right
        
        addArrangedSubview(keyLabel)
        addArrangedSubview(valueStackView)
        
        valueStackView.axis = .horizontal
        valueStackView.spacing = 3.0
        
        let spacer = UIView()
        spacer.setContentHuggingPriority(.defaultLow, for: .horizontal)
        
        valueStackView.addArrangedSubview(spacer)
        valueStackView.addArrangedSubview(valuePrefixContainerView)
        valueStackView.addArrangedSubview(valueLabel)
        
        if drawDebug {
            keyLabel.backgroundColor = UIColor.systemRed
            valueLabel.backgroundColor = UIColor.systemBlue
        }
    }
    
    required init(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    private lazy var valuePrefixContainerView = UIView()
    private var _valuePrefixView: UIView?
    public var valuePrefixView: UIView? {
        get {
            _valuePrefixView
        }
        set {
            _valuePrefixView?.removeFromSuperview()
            _valuePrefixView = newValue
            if let newValue = newValue {
                newValue.translatesAutoresizingMaskIntoConstraints = false
                valuePrefixContainerView.addSubview(newValue)
                
                if let button = newValue as? UIButton {
                    let edges: CGFloat = 4.0
                    button.contentEdgeInsets = UIEdgeInsets(top: edges, left: edges, bottom: edges, right: edges)
                }
                
                NSLayoutConstraint.activate([
                    valuePrefixContainerView.leftAnchor.constraint(equalTo: newValue.leftAnchor),
                    valuePrefixContainerView.topAnchor.constraint(equalTo: newValue.topAnchor),
                    valuePrefixContainerView.rightAnchor.constraint(equalTo: newValue.rightAnchor),
                    valuePrefixContainerView.bottomAnchor.constraint(equalTo: newValue.bottomAnchor)
                ])
            }
        }
    }
    
}

class KVView<Key>: UIStackView where Key: CaseIterable, Key: RawRepresentable, Key.RawValue == String {
    
    private let rows: [Key.RawValue: KVRow<Key>]
    
    private let drawDebug: Bool
    
    init(drawDebug: Bool = false) {
        self.drawDebug = drawDebug
        rows = Key.allCases.reduce(into: [:]) { result, key in
            result[key.rawValue] = KVRow(key: key, drawDebug: drawDebug)
        }
        super.init(frame: .zero)
        axis = .vertical
        spacing = 4.0
        distribution = .fillEqually
        
        Key.allCases.forEach { key in
            let row = rows[key.rawValue]!
            self.addArrangedSubview(row)
        }
    }
    
    required init(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    subscript(key: Key) -> KVRow<Key> {
        rows[key.rawValue]!
    }
    
}