使用委托/协议将数据传递给第三方视图控制器

Question

I have 3 view controllers: http://i58.tinypic.com/2envu2x.png

View Controller 1 is the first, and it segues to view controller 2. view controller 3 is a child view of view controller 2, as there is a container view in view controller2. I need to pass data from view controller 1 to view controller 3. Using traditional delegates and protocols, i have to actually segue to view controller 3 in order to pass data to it. But the segue is from the first view controller to the container view (second view controller), not the third. How can I modify the delegate/protocol to achieve this?

Here is the code for my first view controller (it has a table view so I am putting the protocol in the table cell):

import UIKit

 protocol DataEnteredDelegate {
func userDidCHooseClass(classChose: String)
}

class FirstTableViewCell: UITableViewCell {

var delegate:DataEnteredDelegate?
@IBAction func buttonTapped(sender: AnyObject) {

    let string = "che107"
    self.delegate?.userDidCHooseClass(string)
}




override func awakeFromNib() {
    super.awakeFromNib()
    // Initialization code
}

override func setSelected(selected: Bool, animated: Bool) {
    super.setSelected(selected, animated: animated)

    // Configure the view for the selected state
   }

}

Here is the code for view controller 3, the view controller that I want to receive the string:

  import UIKit

class SecondTBC: UITableViewController, DataEnteredDelegate {

var stringThing = String()

override func viewDidLoad() {
    super.viewDidLoad()

    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem()




}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

// MARK: - Table view data source

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    // #warning Potentially incomplete method implementation.
    // Return the number of sections.
    return 0
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete method implementation.
    // Return the number of rows in the section.
    return 0
}


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("cell1", forIndexPath: indexPath) as! firstCell



    return cell
}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "segue1" {
        var otherController = FirstTableViewCell()
        otherController.delegate = self
    }
}


       func userDidCHooseClass(classChose: String) {
    stringThing = classChose
   }

}

Answer 1

To pass data between two otherwise unconnected View Controllers you'll need to use:

presentingViewController!.dismissViewControllerAnimated(true, completion: nil)

and transmit your data via viewWillDisappear like this:

override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(animated)
    if self.isBeingDismissed() {
        self.delegate?.acceptData(textFieldOutlet.text)
    }
}

I've posted a tutorial , that includes a working project file that you can download and inspect.

---

Heres an example of the pattern in context.

ViewController 2:

// place the protocol in the view controller that is being presented
protocol PresentedViewControllerDelegate {
    func acceptData(data: AnyObject!)
}

class PresentedViewController: UIViewController {
    // create a variable that will recieve / send messages
    // between the view controllers.
    var delegate : PresentedViewControllerDelegate?
    // another data outlet
    var data : AnyObject?


    @IBOutlet weak var textFieldOutlet: UITextField!
    @IBAction func doDismiss(sender: AnyObject) {
        if textFieldOutlet.text != "" {
            self.presentingViewController!.dismissViewControllerAnimated(true, completion: nil)
        }
    }


    override func viewDidLoad() {
        super.viewDidLoad()
        print("\(data!)")

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    override func viewWillDisappear(animated: Bool) {
        super.viewWillDisappear(animated)
        if self.isBeingDismissed() {
            self.delegate?.acceptData(textFieldOutlet.text)
        }
    }

}

ViewController 1:

class ViewController: UIViewController, PresentedViewControllerDelegate {

    @IBOutlet weak var textOutlet: UILabel!
    @IBAction func doPresent(sender: AnyObject) {
        let pvc = storyboard?.instantiateViewControllerWithIdentifier("PresentedViewController") as! PresentedViewController

        pvc.data = "important data sent via delegate!"
        pvc.delegate = self
        self.presentViewController(pvc, animated: true, completion: nil)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

    }

    func acceptData(data: AnyObject!) {     
        self.textOutlet.text = "\(data!)"

    }
}

Answer 2

I have found an answer: using global variables.

Here is what I did:

In my first view controller (the view controller that is sending the string), I made a global variable above the class definition, like this:

 import UIKit

 var chosenClass = String()

 class EntryViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

// other code here that isn't relevant to the topic at hand

}

then, in the same view controller, when a table cell was selected, I did this:

  override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {


    var row = self.tableView.indexPathForSelectedRow()?.row
    chosenClass = array2[row!]




}

where

 array2[row!]

is the string that I am wanting to pass.

in the third view controller, I made another string local variable, string to receive :

import UIKit
import Parse
import ParseUI
import Foundation

 class FirstTableViewController: PFQueryTableViewController {


@IBOutlet weak var navigationBarTop: UINavigationItem!

var stringToRecieve = String()

}

In the viewDidLoad of the third view controller, I simply put:

stringToRecieve = chosenClass

and that is it. No additional code was needed for the second view controller, where the container view is.