UICollectionViewController including type erased delegate

CGSize+Inversed.swift

import UIKit
extension CGSize {
    var inversed: CGSize {
        return CGSize(width: self.height, height: self.width)
    }
}

Device+Kind.swift

extension Device {
    public enum Kind {
        public enum IPhone {
            case four, fourS, iPodTouch4thGen
            case five, fiveS, fiveC, SE, iPodTouch5thGen, iPodTouch6thGen
            case six, sixS, seven, eight
            case sixPlus, sixSPlus, sevenPlus, eightPlus
            case x, xs
            case xr
            case xsmax
        }
        public enum IPad {
            case mini
            case iPad
            case proTenInch
            case proTwelveInch
        }
    }
}

Device+Orientation.swift

extension Device {
    public enum Orientation {
        case horizontal
        case portrait
    }
}

Device+ScreenSizeKind.swift

/*
 https://github.com/Ekhoo/Device/blob/master/Source/Size.swift
 */
extension Device {
    public enum ScreenSizeKind: Int, Comparable {
        case unknownSize = 0
        #if os(iOS)
        /// iPhone 4, 4s, iPod Touch 4th gen.
        case screen3_5Inch
        /// iPhone 5, 5s, 5c, SE, iPod Touch 5-6th gen.
        case screen4Inch
        /// iPhone 6, 6s, 7, 8
        case screen4_7Inch
        /// iPhone 6+, 6s+, 7+, 8+
        case screen5_5Inch
        /// iPhone X, Xs
        case screen5_8Inch
        /// iPhone Xr
        case screen6_1Inch
        /// iPhone Xs Max
        case screen6_5Inch
        /// iPad Mini
        case screen7_9Inch
        /// iPad
        case screen9_7Inch
        /// iPad Pro (10.5-inch)
        case screen10_5Inch
        /// iPad Pro (12.9-inch)
        case screen12_9Inch
        #elseif os(OSX)
        //FIXME: Retina
        case screen11Inch
        case screen12Inch
        case screen13Inch
        case screen15Inch
        case screen17Inch
        case screen20Inch
        case screen21_5Inch
        case screen24Inch
        case screen27Inch
        #endif
    }
}
public func <(lhs: Device.ScreenSizeKind, rhs: Device.ScreenSizeKind) -> Bool {
    return lhs.rawValue < rhs.rawValue
}
public func ==(lhs: Device.ScreenSizeKind, rhs: Device.ScreenSizeKind) -> Bool {
    return lhs.rawValue == rhs.rawValue
}

import UIKit
extension Device.ScreenSizeKind {
    var screenSizePointInPortrait: CGSize {
        switch self {
        case .unknownSize:
            return CGSize(width: 0, height: 0)
            #if os(iOS)
            /// iPhone 4, 4s, iPod Touch 4th gen.
        case .screen3_5Inch:
            return CGSize(width: 320, height: 480)
            
            /// iPhone 5, 5s, 5c, SE, iPod Touch 5-6th gen.
            
        case .screen4Inch://320x568
            return CGSize(width: 320, height: 568)
            
            /// iPhone 6, 6s, 7, 8
        case .screen4_7Inch://375x667
            return CGSize(width: 375, height: 667)
            
            /// iPhone 6+, 6s+, 7+, 8+
        case .screen5_5Inch://414x736
            return CGSize(width: 414, height: 736)
            
            /// iPhone X, Xs
        case .screen5_8Inch://375x812
            return CGSize(width: 375, height: 812)
            
            /// iPhone Xr
        case .screen6_1Inch://414x896
            return CGSize(width: 414, height: 896)
            
            /// iPhone Xs Max
        case .screen6_5Inch://414x896
            return CGSize(width: 414, height: 896)
            
            /// iPad Mini
        case .screen7_9Inch://768x1024
            return CGSize(width: 768, height: 1024)
            
            /// iPad
        case .screen9_7Inch://768x1024
            return CGSize(width: 768, height: 1024)
            
            /// iPad Pro (10.5-inch)
        case .screen10_5Inch://834x1112
            return CGSize(width: 834, height: 1112)
            
            /// iPad Pro (12.9-inch)
        case .screen12_9Inch://1024x1366
            return CGSize(width: 1024, height: 1366)
            
            #elseif os(OSX)
        // FIXME: Size, Retina
        case .screen11Inch:
            return CGSize(width: 0, height: 0)
            
        case .screen12Inch:
            return CGSize(width: 0, height: 0)
            
        case .screen13Inch://e.g. MBA13inch
            return CGSize(width: 1440, height: 900)
            
        case .screen15Inch:
            return CGSize(width: 0, height: 0)
            
        case .screen17Inch:
            return CGSize(width: 0, height: 0)
            
        case .screen20Inch:
            return CGSize(width: 0, height: 0)
            
        case .screen21_5Inch:
            return CGSize(width: 0, height: 0)
            
        case .screen24Inch:
            return CGSize(width: 0, height: 0)
            
        case .screen27Inch:
            return CGSize(width: 0, height: 0)
            
            #endif
        }
    }
}

Device.swift

import UIKit

public enum Device {}
extension Device {
    //機種・端末の向きを指定するとCGSizeが取得できる
    public static func size(device: Kind.IPhone, orientation: Orientation = .portrait) -> CGSize {
        switch orientation {
        case .horizontal:
            return size(device: device).inversed
        case .portrait:
            switch device {
            case .four, .fourS, .iPodTouch4thGen:
                return Device.ScreenSizeKind.screen3_5Inch.screenSizePointInPortrait
            case .five, .fiveS, .fiveC, .SE, .iPodTouch5thGen, .iPodTouch6thGen:
                return Device.ScreenSizeKind.screen4Inch.screenSizePointInPortrait
            case .six, .sixS, .seven, .eight:
                return Device.ScreenSizeKind.screen4_7Inch.screenSizePointInPortrait
            case .sixPlus, .sixSPlus, .sevenPlus, .eightPlus:
                return Device.ScreenSizeKind.screen5_5Inch.screenSizePointInPortrait
            case .x, .xs:
                return Device.ScreenSizeKind.screen5_8Inch.screenSizePointInPortrait
            case .xr:
                return Device.ScreenSizeKind.screen6_1Inch.screenSizePointInPortrait
            case .xsmax:
                return Device.ScreenSizeKind.screen6_5Inch.screenSizePointInPortrait
            }
        }
    }
    public static func size(device: Kind.IPad, orientation: Orientation = .portrait) -> CGSize {
        switch orientation {
        case .horizontal:
            return size(device: device).inversed
        case .portrait:
            switch device {
            case .mini:
                return Device.ScreenSizeKind.screen7_9Inch.screenSizePointInPortrait
            case .iPad:
                return Device.ScreenSizeKind.screen9_7Inch.screenSizePointInPortrait
            case .proTenInch:
                return Device.ScreenSizeKind.screen10_5Inch.screenSizePointInPortrait
            case .proTwelveInch:
                return Device.ScreenSizeKind.screen12_9Inch.screenSizePointInPortrait
            }
        }
    }
}

MyViewController.swift

//: cf: https://gist.github.com/kotowo/a3d16b1033eb0dd1af6e
// https://qiita.com/kazuhiro4949/items/c52fa47d350bec375fae

import UIKit
import PlaygroundSupport

// MARK: MyViewController
class MyViewController<Delegate: MyViewControllerDelegate>: UICollectionViewController, UICollectionViewDelegateFlowLayout {
    // デリゲート先のオブジェクトはAnyMyViewControllerDelegateが持っていて、
    // そこでweakになっているのでここをweakにする必要はない
    var delegate: AnyMyViewControllerDelegate<Delegate>?
    
    var items = [Array<Delegate.Item>]() {
        didSet {
            collectionView?.reloadData()
        }
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // delegateが実装されていなかった時用にとりあえず登録しておく
        collectionView?.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "identifier")
    }
    
    /// セルの登録は初期化の時にcollectionViewを経由せずに行います。
    /// collectionViewに対してクラスを登録するクロージャを使います。初期化の時に型消去クラスも渡してしまうようにします。
    init(_ delegate: AnyMyViewControllerDelegate<Delegate>,
         configure: (_ register: (_ cellClass: AnyClass, _ identifier: String) -> Void) -> Void = { _ in }) {
        super.init(collectionViewLayout: UICollectionViewFlowLayout())
        // CollectionViewに対してセルを登録するクロージャ
        let register = { [weak self] (cellClass: AnyClass, identifier: String) -> Void in
            self?.collectionView?.register(cellClass, forCellWithReuseIdentifier: identifier)
        }
        self.delegate = delegate
        configure(register)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    
    // MARK: UICollectionViewController
    //sectionとrowの数はitemsを元に取る
    override func collectionView(
        _ collectionView: UICollectionView,
        numberOfItemsInSection section: Int) -> Int {
        return items[section].count
    }
    override func numberOfSections(in collectionView: UICollectionView) -> Int {
        return items.count
    }
    // indexPathに対応するデータだけを予め取ってきて、デリゲート先に渡す。
    override func collectionView(
        _ collectionView: UICollectionView,
        cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        //カリー化
        func dequeue(from indexPath: IndexPath)
            -> ((_ identifier: String) -> UICollectionViewCell?) {
                return { (identifier: String) -> UICollectionViewCell? in
                    return self.collectionView.dequeueReusableCell(
                        withReuseIdentifier: identifier, for: indexPath
                    )
                }
        }
        
        let dequeueHandler = dequeue(from: indexPath)
        let item = items[indexPath.section][indexPath.row]
        let cell = delegate?
            .myViewController(
                vc: self,
                dequeue: dequeueHandler,
                cellFor: item
        )
        
        return cell ?? collectionView
            .dequeueReusableCell(
                withReuseIdentifier: "identifier", for: indexPath
        )
    }
    override func collectionView(
        _ collectionView: UICollectionView,
        didSelectItemAt indexPath: IndexPath) {
        delegate?.myViewController(
            vc: self, didSelect: items[indexPath.section][indexPath.row]
        )
    }
    // Layout
    func collectionView(
        _ collectionView: UICollectionView,
        layout collectionViewLayout: UICollectionViewLayout,
        sizeForItemAt indexPath: IndexPath) -> CGSize {
        let contentSize = delegate?
            .myViewController(
                vc: self,
                layout: collectionViewLayout,
                sizeFor: items[indexPath.section][indexPath.row]
        )
        return contentSize ?? collectionViewLayout.collectionViewContentSize
    }
    //セル間のスペースを指定
    func collectionView(
        _ collectionView: UICollectionView,
        layout collectionViewLayout: UICollectionViewLayout,
        minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 1
    }
    
    func collectionView(
        _ collectionView: UICollectionView,
        layout collectionViewLayout: UICollectionViewLayout,
        minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }
}
// MARK: Type Erasure
// MyViewControllerDelegateの型消去クラス。
// Associated TypeをクラスのGenericsへ置き換える。
class AnyMyViewControllerDelegate<Delegate: MyViewControllerDelegate> {
    private weak var delegate: Delegate?
    
    init(delegate: Delegate) {
        self.delegate = delegate
    }
    // MyViewControllerDelegateのメソッドに1対１で対応するメソッドを用意していく
    func myViewController(
        vc: MyViewController<Delegate>,
        dequeue: (_ identifier: String) -> UICollectionViewCell?,
        cellFor item: Delegate.Item) -> UICollectionViewCell? {
        return delegate?.myViewController(vc: vc, dequeue: dequeue, cellFor: item)
    }
    
    func myViewController(
        vc: MyViewController<Delegate>,
        layout collectionViewLayout: UICollectionViewLayout,
        sizeFor item: Delegate.Item) -> CGSize? {
        return delegate?.myViewController(vc: vc, layout: collectionViewLayout, sizeFor: item)
    }
    
    func myViewController(
        vc: MyViewController<Delegate>,
        didSelect item: Delegate.Item) {
        delegate?.myViewController(vc: vc, didSelect: item)
    }
}
// MARK: MyViewControllerDelegate
protocol MyViewControllerDelegate: class {
    associatedtype Item //セルに渡すデータの型
    
    func myViewController(
        vc: MyViewController<Self>,
        dequeue: ((_ identifier: String) -> UICollectionViewCell?),
        cellFor item: Item) -> UICollectionViewCell?
    
    func myViewController(
        vc: MyViewController<Self>,
        layout collectionViewLayout: UICollectionViewLayout,
        sizeFor item: Item) -> CGSize?
    
    func myViewController(
        vc: MyViewController<Self>,
        didSelect item: Item)
}

extension MyViewControllerDelegate {
    func myViewController(vc: MyViewController<Self>, layout collectionViewLayout: UICollectionViewLayout, sizeFor item: Item) -> CGSize? { return nil }
    func myViewController(vc: MyViewController<Self>, didSelect item: Item) {}
}

// #################################################
// Create sample ViewController the above Framework
// It has types of cell in CollectionView.
// #################################################

enum Element {
    case banner(name: String)
    case content(name: String)
    case ad(name: String) // 広告コンテンツを追加
}

/// MyViewControllerを子クラスとして持ち、MyViewControllerのDelegate先として使われる
final class ViewController: UIViewController {
    static let cellIdentifier = "cell"
    typealias Item = Element
    
    lazy var childVc: MyViewController<ViewController> = {
        return MyViewController(
        AnyMyViewControllerDelegate(delegate: self)) { (register) in
            register(UICollectionViewCell.self, ViewController.cellIdentifier)
        }
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        title = "Title"
        
        addChild(childVc)
        childVc.view.frame = view.bounds
        childVc.view.autoresizingMask = [.flexibleHeight, .flexibleWidth]
        view.addSubview(childVc.view)
        childVc.didMove(toParent: self)
        
        childVc.items = [[
            .banner(name: "バナー"),
            .content(name: "コンテンツ"), .content(name: "コンテンツ"),
            .ad(name: "広告"),
            .content(name: "コンテンツ"), .content(name: "コンテンツ"),
            .ad(name: "広告"),
            .content(name: "コンテンツ"), .content(name: "コンテンツ"),
            .ad(name: "広告"),
            .content(name: "コンテンツ"), .content(name: "コンテンツ"),
            .ad(name: "広告")
            ]]
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}
// MARK:- MyViewControllerDelegate
extension ViewController: MyViewControllerDelegate {
    static let bannerHeight: CGFloat = 60
    
    func myViewController(
        vc: MyViewController<ViewController>,
        dequeue: ((_ identifier: String) -> UICollectionViewCell?),
        cellFor item: Item) -> UICollectionViewCell? {
        let cell = dequeue(ViewController.cellIdentifier)
        switch item {
        case .banner(_):
            cell?.backgroundColor = .red
        case .content(_):
            cell?.backgroundColor = .white
        case .ad(_):
            cell?.backgroundColor = .blue
        }
        return cell
    }
    
    func myViewController(
        vc: MyViewController<ViewController>,
        layout collectionViewLayout: UICollectionViewLayout,
        sizeFor item: Item) -> CGSize? {
        let contentLength = Int(vc.view.frame.width) / 2
        switch item {
        case .banner(_):
            return CGSize(
                width: vc.view.frame.width,
                height: ViewController.bannerHeight
            )
        case .content(_), .ad(_):
            return CGSize(
                width: contentLength,
                height: contentLength
            )
        }
    }
}
// MARK: Configure Playground Page
PlaygroundPage.current.needsIndefiniteExecution = true

// MARK: 直接 liveViewの画面サイズを指定
let navVC = UINavigationController(rootViewController: ViewController())
navVC.view.frame = CGRect(x: 0, y: 0, width: 375, height: 812)//iPhone X
PlaygroundPage.current.liveView = navVC.view

// MARK: LiveViewの画面サイズを端末種別で指定するオプション
/// 指定された端末の画面サイズでLiveviewを設定する
///
/// - Parameter device: iPhoneの端末種別
//func configurePlaygroundPageLiveView(for device: Device.Kind.IPhone = .x) {
//    let nc = UINavigationController(rootViewController: ViewController())
//    let deviceSize = Device.size(device: device)
//    nc.view.frame = CGRect(x: 0, y: 0, width: deviceSize.width, height: deviceSize.height)
//    PlaygroundPage.current.liveView = nc.view
//}
//configurePlaygroundPageLiveView()