A playground file that contains an example of making a protocol datasource in Swift.

DataSourceSample.playground

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

import UIKit

// DATA SOURCE EXAMPLE:

/** This MyViewDataSource protocol is just like the UITableViewDataSource
 */
protocol MyViewDataSource {
    func increment(count: Int) -> Int
}

/** MyView is like the UITableView
 */

class MyView {
    var count = 0
    var dataSource: MyViewDataSource!
    
    func reloadData() {
        if let amount = dataSource?.increment(count: count) {
            count += amount
            print("COUNT: \(count)")
        }
    }
}

/** MainClass is your UIViewController
 */

class MainClass {
    let myView = MyView()
    
    func load() {
        self.myView.dataSource = self
        self.myView.reloadData()
    }
}

/** Just an extension of MainClass (your controller) conforming to the dataSource.
 */

extension MainClass: MyViewDataSource {
    /** Conform to the MyViewDataSource.
     *  This function is just like the CellForRow of the UITableViewDataSource
     */
    func increment(count: Int) -> Int {
        return 5
    }
}

/** Now to execute this example, make a new instance of MainClass or your Controller and execute the load().
 *  The load() function is just like your controller's viewDidLoad function.
 */

let mainClass = MainClass()
mainClass.load()