Reusable.swift

import UIKit

public protocol Reusable {
    static var reuseIdentifier: String { get }
}

public extension Reusable {
    static var reuseIdentifier: String {
        return String(describing: self)
    }
}

extension UITableViewCell: Reusable {}
extension UICollectionViewCell: Reusable {}
extension UITableViewHeaderFooterView: Reusable {}

public extension UITableView {
    
    final func register<T: UITableViewCell>(cellType: T.Type) {
        register(
            cellType.self,
            forCellReuseIdentifier: cellType.reuseIdentifier
        )
    }
    
    final func dequeueReusableCell<T: UITableViewCell>(
        for indexPath: IndexPath,
        cellType: T.Type = T.self
    ) -> T {
        guard let cell = self.dequeueReusableCell(
                withIdentifier: cellType.reuseIdentifier,
                for: indexPath) as? T
        else {
            assertionFailure(
                """
                Failed to dequeue a cell with identifier \(cellType.reuseIdentifier)
                matching type \(cellType.self).

                Check that the reuseIdentifier is set properly in your XIB/Storyboard
                and that you registered the cell beforehand
                """
            )
            return T()
        }
        return cell
    }
    
    final func register<T: UITableViewHeaderFooterView>(headerFooterViewType: T.Type) {
        register(
            headerFooterViewType.self,
            forHeaderFooterViewReuseIdentifier: headerFooterViewType.reuseIdentifier
        )
    }
    
    final func dequeueReusableHeaderFooterView<T: UITableViewHeaderFooterView>(
        _ viewType: T.Type = T.self
    ) -> T? {
        guard let view = dequeueReusableHeaderFooterView(
                withIdentifier: viewType.reuseIdentifier) as? T?
        else {
            assertionFailure(
                """
                Failed to dequeue a header/footer with identifier \(viewType.reuseIdentifier)
                matching type \(viewType.self).

                Check that the reuseIdentifier is set properly in your XIB/Storyboard
                and that you registered the header/footer beforehand
                """
            )
            return T()
        }
        return view
    }
}

public extension UICollectionView {
    
    final func register<T: UICollectionViewCell>(cellType: T.Type) {
        register(
            cellType.self,
            forCellWithReuseIdentifier: cellType.reuseIdentifier
        )
    }
    
    final func dequeueReusableCell<T: UICollectionViewCell>(
        for indexPath: IndexPath,
        cellType: T.Type = T.self
    ) -> T {
        guard let cell = dequeueReusableCell(
                withReuseIdentifier: cellType.reuseIdentifier,
                for: indexPath) as? T else {
            assertionFailure(
                """
                Failed to dequeue a cell with identifier \(cellType.reuseIdentifier)
                matching type \(cellType.self).

                Check that the reuseIdentifier is set properly in your XIB/Storyboard
                and that you registered the cell beforehand
                """
            )
            return T()
        }
        return cell
    }
    
    final func register<T: UICollectionReusableView>(
        supplementaryViewType: T.Type,
        ofKind elementKind: String
    ) where T: Reusable {
        register(
            supplementaryViewType.self,
            forSupplementaryViewOfKind: elementKind,
            withReuseIdentifier: supplementaryViewType.reuseIdentifier
        )
    }
    
    final func dequeueReusableSupplementaryView<T: UICollectionReusableView>(
        ofKind elementKind: String,
        for indexPath: IndexPath,
        viewType: T.Type = T.self
    ) -> T where T: Reusable {
        let view = dequeueReusableSupplementaryView(
            ofKind: elementKind,
            withReuseIdentifier: viewType.reuseIdentifier,
            for: indexPath
        )
        guard let typedView = view as? T else {
            assertionFailure(
                """
                Failed to dequeue a supplementary view with identifier \(viewType.reuseIdentifier)
                matching type \(viewType.self).

                Check that the reuseIdentifier is set properly in your XIB/Storyboard
                and that you registered the supplementary view beforehand
                """
            )
            return T()
        }
        return typedView
    }
}