ScrollingStackView.swift

//
//  ScrollingStackView.swift
//  ScrollingStackView
//
//  Created by Andreas Alfarè on 14.08.18.
//  Copyright © 2018 Andreas Alfarè. All rights reserved.
//

import UIKit

class ScrollingStackView: UIScrollView {
    var axis: UILayoutConstraintAxis {
        get {
            return contentView.axis
        }
        set {
            contentView.axis = newValue
            setNeedsUpdateConstraints()
        }
    }
    
    lazy var contentView: UIStackView = {
        let contentView = UIStackView()
        contentView.translatesAutoresizingMaskIntoConstraints = false
        return contentView
    }()
    
    convenience init() {
        self.init(axis: .vertical)
    }
    
    convenience init(axis: UILayoutConstraintAxis = .vertical) {
        self.init(frame: .zero)
        contentView.axis = axis
        setup()
    }
    
    private lazy var verticalConstraints: [NSLayoutConstraint] = {
        return [
            contentView.widthAnchor.constraint(equalTo: widthAnchor),
        ]
    }()
    
    private lazy var horizontalConstraints: [NSLayoutConstraint] = {
        return [
            contentView.heightAnchor.constraint(equalTo: heightAnchor),
        ]
    }()
    
    private func setup() {
        addSubview(contentView)
        NSLayoutConstraint.activate([
            contentView.topAnchor.constraint(equalTo: topAnchor),
            contentView.leadingAnchor.constraint(equalTo: leadingAnchor),
            contentView.trailingAnchor.constraint(equalTo: trailingAnchor),
            contentView.bottomAnchor.constraint(equalTo: bottomAnchor),
        ])
    }
    
    override func updateConstraints() {
        switch axis {
        case .horizontal:
            NSLayoutConstraint.deactivate(verticalConstraints)
            NSLayoutConstraint.activate(horizontalConstraints)
        case .vertical:
           NSLayoutConstraint.deactivate(horizontalConstraints)
           NSLayoutConstraint.activate(verticalConstraints)
        }
        
        alwaysBounceVertical = axis == .vertical
        alwaysBounceHorizontal = axis == .horizontal
        
        super.updateConstraints()
    }
}