Create generic table/collection controllers

[tylermilner]

I know most of our projects typically separate out table/collection view functionality into separate objects. We should take this a step further and make some generic controllers to handle this (which I think some projects already do). Since SwiftUI is coming (eventually), we shouldn't spend too much time on it, but at least handling the basic case of presenting a list of identical cells should be a goal.

I spent a few minutes doodling so here's something to get started:

class CollectionController<ItemType, CellType: UICollectionViewCell>: NSObject, UICollectionViewDataSource {
    
    private let items: [ItemType]
    private let cellConfigurationBlock: (ItemType, CellType) -> Void
    
    init(items: [ItemType], cellConfigurationBlock: @escaping (ItemType, CellType) -> Void) {
        self.items = items
        self.cellConfigurationBlock = cellConfigurationBlock
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return items.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: String(describing: CellType.self), for: indexPath) as? CellType else { fatalError("Unable to dequeue cell of type '\(CellType.self)'") }
        
        let item = items[indexPath.item]
        cellConfigurationBlock(item, cell)
        
        return cell
    }
}