LiulietLee's ProgmLayout (Modified).swift

//
//  ViewController.swift
//  layout
//
//  Created by Liuliet.Lee on 10/8/2017.
//  Copyright © 2017 Liuliet.Lee. All rights reserved.
//
import UIKit

class ViewController: UIViewController {
    // MARK: Subviews
    private lazy var viewDict: [String: UIView] = [
        "fadeButton": self.button(bColor: .darkGray, title: "fade", selector: #selector(fade)),
        "gap": UIView(),
        "moveButton": self.button(bColor: .orange, title: "move", selector: #selector(move))
    ]

    private var fadeButton: UIView! { return viewDict["fadeButton"] }
    private var gap: UIView! { return viewDict["gap"] }
    private var moveButton: UIView! { return viewDict["moveButton"] }

    // MARK: Constraints
    private lazy var cons: [NSLayoutConstraint] = [
        self.fadeButton.widthAnchor.constraint(equalToConstant: 200.0),
        self.fadeButton.heightAnchor.constraint(equalToConstant: 100.0),
        self.moveButton.widthAnchor.constraint(equalTo: self.fadeButton.widthAnchor),
        self.moveButton.heightAnchor.constraint(equalTo: self.fadeButton.heightAnchor),
        self.gap.centerXAnchor.constraint(equalTo: self.view.centerXAnchor),
        self.gap.centerYAnchor.constraint(equalTo: self.view.centerYAnchor)
    ]

    private var currentAdditionalCons = [NSLayoutConstraint]()
    private lazy var vCons: [NSLayoutConstraint] = NSLayoutConstraint.constraints(withVisualFormat: "V:[fadeButton]-[gap(==160)]-[moveButton]", options: [.alignAllCenterX], metrics: nil, views: self.viewDict)
    private lazy var hCons: [NSLayoutConstraint] = NSLayoutConstraint.constraints(withVisualFormat: "H:[fadeButton]-[gap(==300)]-[moveButton]", options: [.alignAllCenterY], metrics: nil, views: self.viewDict)

    @objc private func configureConstraints() {
        NSLayoutConstraint.deactivate(currentAdditionalCons)
        defer { NSLayoutConstraint.activate(currentAdditionalCons) }
        if traitCollection.horizontalSizeClass == .compact
            || !UIDevice.current.orientation.isLandscape {
            currentAdditionalCons = vCons
        } else {
            currentAdditionalCons = hCons
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        for subview in viewDict.values {
            // Important: Must disable autoresizing mask
            subview.translatesAutoresizingMaskIntoConstraints = false
            view.addSubview(subview)
        }
        NSLayoutConstraint.activate(cons)
        // MARK: Update Observers
        NotificationCenter.default.addObserver(self, selector: #selector(configureConstraints), name: .UIDeviceOrientationDidChange, object: nil)
    }

    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        super.traitCollectionDidChange(previousTraitCollection)
        configureConstraints()
    }

    // MARK: Auxiliary
    private func button(bColor: UIColor, title: String, selector: Selector) -> UIButton {
        let button = UIButton()
        button.translatesAutoresizingMaskIntoConstraints = false
        button.backgroundColor = bColor
        button.setTitleColor(.white, for: .normal)
        button.setTitle(title, for: .normal)
        button.titleLabel?.font = UIFont(name: "Avenir", size: 36.0)
        button.layer.cornerRadius = 16.0
        button.addTarget(self, action: selector, for: .touchUpInside)
        return button
    }

    @objc private func fade() {
        UIView.animate(withDuration: 0.6, delay: 0.0, options: [.autoreverse],
                       animations: { self.fadeButton.alpha = 0.0 },
                       completion: { isFinished in if isFinished { self.fadeButton.alpha = 1.0 } })
    }

    @objc private func move() {
        UIView.animate(withDuration: 0.6, delay: 0.0, options: [.autoreverse],
                       animations: { self.moveButton.frame.origin.y += 100.0 },
                       completion: { isFinished in if isFinished { self.moveButton.frame.origin.y -= 100.0 } })
    }
}

extension UIDeviceOrientation {
    fileprivate var isLandscape: Bool {
        return self == .landscapeLeft || self == .landscapeRight
    }
}