silly.swift

//: Playground - noun: a place where people can play

import UIKit

public protocol Constructible {
    init()
}

public final class MyDataSource<T: Constructible>: NSObject, UICollectionViewDataSource  {
    var x = T()

    public func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
         return 1
    }
    
    public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        return UICollectionViewCell()
    }
    
    
}

public class MyCollectionViewController<T: Constructible>: UICollectionViewController {
    
    public override func viewDidLoad() {
        super.viewDidLoad()
        
        collectionView?.dataSource = MyDataSource<T>()
    }
    
}

public func doSomethingWithVC<T>(vc: MyCollectionViewController<T>) {
    
}

extension String: Constructible {}

let vc = MyCollectionViewController<String>()
doSomethingWithVC(vc: vc)