Passing date back from view controller

Question

I've been following this thread at the end the code doesn't show any errors but when I run it on my phone, the application crashes and I get a signal SIGABRT error, what could be causing it? This is my code:

FirstViewController.swift :

class FirstViewController: UIViewController, UITextFieldDelegate, setDateValueDelegate{

func setDate(value: String) {
    self.receivedDate = value
}

@IBOutlet weak var dateButton: UIButton!
var receivedDate:String = ""

 override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    var secondVC = (segue.destinationViewController.visibleViewController as  SecondViewController)
    secondVC.delegate = self
}

SecondViewController.swift:

protocol setDateValueDelegate {
  func setDate(value: String)
}

class SecondViewController: UIViewController {

var delegate: setDateValueDelegate?
@IBOutlet weak var datePicker: UIDatePicker!

var strDate:String = ""

func datePickerChanged(datePicker:UIDatePicker) {
    var dateFormatter = NSDateFormatter()

    dateFormatter.dateStyle = NSDateFormatterStyle.ShortStyle
    dateFormatter.timeStyle = NSDateFormatterStyle.ShortStyle

    strDate = dateFormatter.stringFromDate(datePicker.date)
    dateLabel.text = strDate

    delegate?.setDate(strDate)
}

Any help is appreciated! :)

Is the class called DatePickerViewController or SecondViewController? — Lyndsey Scott, Dec 24 '14 at 03:51
@LyndseyScott fixed! Its actual name is DatePickerViewController but it was replaced in the post for making it more simpler to read by the users over here. — Omar Dlhz, Dec 24 '14 at 03:55
@LyndseyScott oh, the problem persists, what I fixed was the name of the ViewController, it was actually a typo. — Omar Dlhz, Dec 24 '14 at 03:58
Gotcha. At what point do you actually get the error? When setting the date? — Lyndsey Scott, Dec 24 '14 at 04:05
Oh, I see. You never actually set the delegate on the active Second View Controller since it's not visible yet during `prepareForSegue`. — Lyndsey Scott, Dec 24 '14 at 04:09
@LyndseyScott Actually my Storyboard consists like this: To-Do List has an add button, when pressed it takes to FirstViewController and it has a button which takes to SecondViewController. The error happens when I press the add button. — Omar Dlhz, Dec 24 '14 at 04:16
I'm not sure you're understanding me... I'll write up an answer to explain. — Lyndsey Scott, Dec 24 '14 at 04:17

Lyndsey Scott · Answer 1 · 2014-12-24T05:07:31.403

0

Since it's not actually "visible" yet, your segue.destinationViewController.visibleViewController line doesn't work to get an instance of the soon-to-be-active SecondViewController instance; and as such, I believe the problem is that you never actually set the delegate.

Try updating your prepareForSegue method by removing the visibleViewController property and simply get the segue's destinationViewController, like so:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    var secondVC = segue.destinationViewController as  SecondViewController
    secondVC.delegate = self
}

Edit: Also try setting your delegate's protocol at the top of SecondViewController if you haven't already:

// set up the setDateValueDelegate protocol with the set date function
protocol setDateValueDelegate {
    func setDate(value: String)
}

class SecondViewController: UIViewController {

    var delegate: setDateValueDelegate?

edited Dec 24 '14 at 05:07

answered Dec 24 '14 at 04:20

Lyndsey Scott

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I removed the visibleViewController and the app still crashes :( – Omar Dlhz Dec 24 '14 at 04:28
@OmarDlhz Is the text you've added to `dateLabel` in your `datePickerChanged` method showing up correctly? – Lyndsey Scott Dec 24 '14 at 04:32
yes, the text was showing up correctly before I tried to pass data from one VC to the other. – Omar Dlhz Dec 24 '14 at 04:34
where and how? Sorry for my ignorance. I have a separate file called protocol.swift – Omar Dlhz Dec 24 '14 at 04:54
Oh, I see you already have that code in your protocol. Did you import it? Maybe that's not the issue then... I'll let you know if I think of anything else... – Lyndsey Scott Dec 24 '14 at 05:06
removed the protocol.swift file and added the delegates protocol to the top of the SecondVC and an error appeared in "delegate?.setDate(strDate)" value of optional type string not wrapped. – Omar Dlhz Dec 24 '14 at 05:06
@OmarDlhz remove the "optional" before func then in the protocol – Lyndsey Scott Dec 24 '14 at 05:07
@OmarDlhz I think you should put in some breakpoints to identify the exact line that's giving you the issue. – Lyndsey Scott Dec 24 '14 at 15:48
I already fixed the error! I'm going to post the answer over here. – Omar Dlhz Dec 24 '14 at 16:58

score 0 · Accepted Answer · answered Jan 02 '15 at 05:44

So, Im going to answer my own question and at the same time answer it to any other person who want to pass data from ViewController B to ViewController A. I will try to describe every detail for making it more simple step by step.

In your storyboard, give an identifier to your segue, this is done by clicking on the segue and going to the Attributes Inspector.
Create a file called "protocol.swift" with the following code inside.

protocol.swift :

protocol setDateValueDelegate {
func setDate(toValue: String)
}

The "setDateValueDelegate" and "setDate" can be replaced to whatever you want but they must be consistent within the entire code.

In your FirstViewController class, implement the protocol.

FirstViewController.swift:

class FirstViewController: UIViewController, setDateValueDelegate {

(The protocols name, in my case "setDateValueDelegate" must be the same as the one in protocol.swift)

Add the function to your first view controller.

func setDate(toValue:String) {  //setDate must be replaced to the name of your function in the protocol.swift file.
var date = toValue // The value that is being received from the SecondViewController.

}

Add prepareForSegue function to your FirstViewController:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier == "DueDate") {

var secondVC: SecondViewController = (segue.destinationViewController as SecondViewController)

secondVC.delegate = self

}

(SecondViewController in "var secondVC: SecondViewController" and in "as SecondViewController" must be replaced to your Second View Controller's name.

Add the delegate in SecondViewController

var delegate:setDateValueDelegate?
/* As before setDateValueDelegate must be replaced to the name that
you gave to your delegate */

In your Second View Controller's ViewDidLoad call the delegate:
```
    delegate?.setDate(/* The value that you want to send to the FirstViewController*/)
```
/* setDate must be changed to the function's name in protocol.swift */

Hope this helped to you all! :)

score 0 · Answer 3 · answered Jan 23 '15 at 13:46

I did it like this

FirstViewController:

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

    var SecondVC: SecondViewController = segue.destinationViewController as SecondViewController

    if segue.identifier == "Player2Button"{
        SecondVC.NumberOfPlayers = 2
    }else{
        SecondVC.NumberOfPlayers = 1
    }

}

SecondViewController

Just use NumberOfPlayers to do whatever you want. Hope this helps

Passing date back from view controller

3 Answers3