CollectionViewModel.swift

// MARK: - Setup Logic

extension CollectionViewModel {
    private func cellProvider(_ collectionView: UICollectionView, indexPath: IndexPath, item: Item) -> UICollectionViewCell? {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath) as! CellType
        cell.provide(item)
        return cell
    }
    
    public func makeDataSource() -> DataSource {
        guard let collectionView = collectionView else { fatalError("CollectionView isn't here :(") }
        let dataSource = DataSource(collectionView: collectionView, cellProvider: cellProvider)
        self.dataSource = dataSource
        return dataSource
    }
}