当数据源和委托与View Controller分开时，如何将Table View的单击项发送到其他View Controller

Question

I am a beginner to iOS coming from the android background and just learned about table view (for me it's an Android ListView). I am trying to separate data source & delegate from view controller. I found some tutorials on how to do so but stuck at figuring out how to send the clicked item to another view controller. The code is below:

class PictureTableViewController: UIViewController {


    @IBOutlet weak var pictureTableView: UITableView!

    private let picsDataSource: PicturesDataSource

    required init?(coder aDecoder: NSCoder) {
        self.picsDataSource = PicturesDataSource()
        super.init(coder: aDecoder)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        pictureTableView.dataSource = picsDataSource
        pictureTableView.reloadData()
        pictureTableView.delegate = picsDataSource
    }
}

class PicturesDataSource: NSObject, UITableViewDataSource, UITableViewDelegate{

    private var pictureModels = [PictureModel]()

    override init(){
        let picModelsDataController = PictureModelsDataController()
        pictureModels = picModelsDataController.pictureModels
    }


    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return pictureModels.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PictureCell.self)) as! PictureCell

        let picModel = pictureModels[indexPath.row]
        cell.pictureName = picModel.pictureName
        cell.imageItem = picModel.imageItem

        return cell
    }

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {


        //1 - try loading the "Detail" view controller and typecasting it to be DetailViewController
        if let detailViewController = storyboard.instantiateViewController(withIdentifier: "PictureDetailView") as? PictureDetailViewController {

            //2 - success! set its selecteImage property
            detailViewController.selectedImgName = pictureModels[indexPath.row].pictureName

            //3 - now push it onto the navigation controller
            navigationController?.pushViewController(detailViewController, animated: true)
        }
    }

}     

Error in: func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath){ } . since "storyboard" & "navigationController" are not available in PicturesDataSource class, how can I send clicked item(picture name) to the DetailsViewController

There are StackOverflow answers about separating data source and delegate but did not solve my problem.

Using: Xcode 8.3 beta 6

Answer 1

You can include a reference to main view controller at your table view events handler. Below is a playground code I derived from your example:

import UIKit

// MARK: - Model

struct Picture {
  let title: String
  let image: UIImage
}

struct PictureModelsDataSource {
  let pictures = [
    Picture(title: "exampleTitle", image: UIImage(named: "exampleImage")!),
    Picture(title: "exampleTitle", image: UIImage(named: "exampleImage")!)
  ]
}

// MARK - View

class PictureCell: UITableViewCell {
  @IBOutlet weak var pictureTitleLabel: UILabel!
  @IBOutlet weak var pictureImage: UIImageView!
}

// MARK: - Controller

class PictureTableViewController: UIViewController {

  // MARK: - Properties

  @IBOutlet weak var pictureTableView: UITableView!

  private var pictureListController: PictureListController?

  // MARK: - View lifecycle

  override func viewDidLoad() {
    super.viewDidLoad()
    pictureListController = PictureListController()
    pictureListController?.viewController = self
    pictureTableView.dataSource = pictureListController
    pictureTableView.delegate = pictureListController
    pictureTableView.reloadData()
  }
}

class PictureDetailViewController: UIViewController {
  var selectedPictureTitle: String?
}

class PictureListController: NSObject, UITableViewDataSource, UITableViewDelegate {

  // MARK: - Properties

  weak var viewController: PictureTableViewController?

  private let pictures: [Picture] = {
    let pictureModelsDataSource = PictureModelsDataSource()
    return pictureModelsDataSource.pictures
  }()

  // MARK: - View setup

  func numberOfSections(in tableView: UITableView) -> Int {
    return 1
  }

  // MARK: - Event handling

  func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return pictures.count
  }

  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    guard let cell = tableView.dequeueReusableCell(withIdentifier: String(describing: PictureCell.self)) as? PictureCell else {
      return UITableViewCell()
    }

    let picture = pictures[indexPath.row]
    cell.pictureTitleLabel.text = picture.title
    cell.pictureImage.image = picture.image

    return cell
  }

  func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let pictureTitle = pictures[indexPath.row].title
    let storyboard = UIStoryboard(name: "exampleStoryboard", bundle: nil)
    if let pictureDetailViewController = storyboard.instantiateViewController(withIdentifier: "PictureDetailView") as? PictureDetailViewController {
      pictureDetailViewController.selectedPictureTitle = pictureTitle
      viewController?.navigationController?.pushViewController(pictureDetailViewController, animated: true)
    }
  }
}

Answer 2

See StoryBoard object can be obtained by using this

let storyboard : UIStoryboard = UIStoryboard(name: "Main", bundle: nil)

Now your second question is about how to get navigation controller. It means how to get currentViewController in your case. This can be get by below code

 func getCurrentViewController() -> UIViewController? {

 if let rootController = UIApplication.shared.keyWindow?.rootViewController {
    var currentController: UIViewController! = rootController
       while( currentController.presentedViewController != nil ) {
                currentController = currentController.presentedViewController
            }
            return currentController
        }
        return nil
    }

Now your didSelectRowAt code will look like this

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
 let storyboard : UIStoryboard = UIStoryboard(name: "Main", bundle: nil)

 if let detailViewController = storyboard.instantiateViewController(withIdentifier: "PictureDetailView") as? PictureDetailViewController 
   detailViewController.selectedImgName = pictureModels[indexPath.row].pictureName
    self.getCurrentViewController()!.pushViewController(detailViewController, animated: true)  
}

Answer 3

You are trying to adhere to MVC, but you are confusing what your actual data source is.

PicturesDataSource is not your data source . It's the code that tells your table how to set itself up.

PictureModelsDataController() is the source from which you get the data that actually populates that table.

---

All of your posted code should be in the same class:

class PictureTableViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

---

Change these lines:

pictureTableView.dataSource = picsDataSource
pictureTableView.delegate = picsDataSource

to

pictureTableView.dataSource = self  // Note use of self because this is now the dataSource, not another class
pictureTableView.delegate = self  // Note use of self because this is now the delegate, not another class

and remove:

private let picsDataSource: PicturesDataSource

required init?(coder aDecoder: NSCoder) {
    self.picsDataSource = PicturesDataSource()
    super.init(coder: aDecoder)
}