Delegate and Datasource in different classes possible? - UITableView

Question

While using UITableView there are two types of methods ie, datasource and delegates still both supposed to be connected to the same parent view controller class.

Is there any way to define delegates and datasources in diffrent classes?

Why we need seperation as delegates and datasources?

Note: This question applies to UICollectionView and similar Objects

Answer 1

As explained well enough about the delegation pattern in other responses, we can declare tableview Datasource and Delegate as different objects in order to avoid Massive ViewControllers and to achieve lean ViewControllers .

Here is a code example Using Delegate Design pattern .

import UIKit

// MARK: Cell

class ItemCell: UITableViewCell{
    var label: UILabel!
    override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 20))
        label.textColor = .black
        label.backgroundColor = .yellow
        contentView.addSubview(label)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

// MARK: Main View Controller

class BlueViewController: UIViewController{

    var tableView: UITableView!
    var myDataSourse: MyTVDataSource!
    var myDelegate: MyTVDelegate!


    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .blue
        tableView = UITableView()
        myDataSourse = MyTVDataSource(tableView: tableView)
        myDelegate = MyTVDelegate()
        myDelegate.presentingController = self
        tableView.dataSource = myDataSourse
        tableView.delegate = myDelegate
        tableView.register(ItemCell.self, forCellReuseIdentifier: "Cell")

        self.view.addSubview(tableView)



        self.tableView.translatesAutoresizingMaskIntoConstraints = false

        NSLayoutConstraint.activate([
            tableView.topAnchor.constraint(equalTo: view.topAnchor, constant: 0),
            tableView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0),
            tableView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0),
            tableView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 0)
            ])
    }
}
extension BlueViewController: BluePresenting{
    func currentSelected(_ indexPath: IndexPath) {
        print(indexPath)
    }


}

// MARK: TableViewDelegate


protocol BluePresenting: class {
    func currentSelected(_ indexPath: IndexPath)
}

class MyTVDelegate: NSObject,UITableViewDelegate{

   var presentingController: BluePresenting?

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
            presentingController?.currentSelected(indexPath)
    }
}

// MARK: TableView DataSource


class MyTVDataSource: NSObject, UITableViewDataSource{
    private var tableView: UITableView
    private var items = ["Item 1","item 2","item 3","Item 4"]

    init(tableView: UITableView) {
        self.tableView = tableView
    }
    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return items.count

    }
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = ItemCell(style: .default, reuseIdentifier: "Cell")
        cell.label.text = items[indexPath.row]

        return cell
    }

}

Answer 2

Yes you can have them in separate classes. They are normally in the same class because you may need to use data(like array) inside delegate methods like in didSelectRowAtIndexPath:

Tableview and Collectionview Datasource and Delegates are based on Delegate design pattern, where you can delegate some work to other objects.

Why do you need two different protocols?

Because datasource is used to provide data that controls the state of the tableview/collectionview whereas delegate supplies behaviour and controls how to use the data.