Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Build a Playlist Browser with Swift Using a Navigation Controller With Segues Modifying the UI

Posted by Steven Ossorio
Steven Ossorio
1,706 Points

Having issue with prepareForSegue. Please help

My PlayListMasterViewController.swift is 

import UIKit

class PlaylistMasterViewController: UIViewController {

    @IBOutlet weak var aButton: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        aButton.setTitle("Press me!", forState: .Normal)

}

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

override func prepareForSegue(segue: UIStoryboardSegue, sender:  AnyObject?) {
        if segue.identifier == "showPlaylistDetail" {
            let playListDetailedController = segue.destinationViewController as  PlaylistDetailViewController
        }
    }
}

Currently I get an error on line 30 let playListDetailController = segue.destinationViewController as PlaylistDetailViewController. The error says: 

'UIViewController' is not convertible to 'PlaylistDetailViewController'; 
did you mean to use 'as!' to force do...

In the lesson video there wasn't any error which would require an as!. Did I mess up my code somewhere that I haven't realized?

Incase it's required my PlayListDetailViewController.swift code is:

import UIKit

class PlaylistDetailViewController: UIViewController {

    @IBOutlet weak var buttonPressedLabel: UILabel!


    override func viewDidLoad() {
        super.viewDidLoad()

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

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
huckleberry
huckleberry
14,636 Points
huckleberry
huckleberry
14,636 Points

Added formatting to your code there for ya. In the future, wrap your code with 3 backticks (these ```... they're the key next to the 1) before and after your code. For language specific syntax, put the name of the language after the 3 beginning backticks.

here is a more detailed explanation of everything.

Cheers,

Huck - :sunglasses:

5 Answers

Nicoara Talpes
Nicoara Talpes
7,354 Points
Nicoara Talpes
Nicoara Talpes
7,354 Points

using as! works for me.

Martin Wildfeuer
PLUS
Martin Wildfeuer
Courses Plus Student 11,071 Points
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points

This most likely means you have not set the custom class of your destination view controller in storyboard. Select your view controller in storyboard, bring up the Utilities tab (upper right) -> Identity inspector and insert your custom class name (PlaylistDetailViewController) in Custom class -> Class.

Let me know if that helps :)

Steven Ossorio
Steven Ossorio
1,706 Points

Hello Martin. Thank you for replying to my question. I checked my code today and it's already set as you've mentioned. When I select the originally view controller which has been renamed to PlaylistMasterController, the custom class is set to PlaylistMasterController. Same is set for the detail one such as PlaylistDetailViewController. Any ideas why it might be failing? if you need more info regarding what I've done thus far, please ask.

Thank you again for your help.

Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points

Hey everyone!

Let's give it a try, where do you end up with unwrapping? Yep or Nope?

if let playListDetailedController = segue.destinationViewController as? PlaylistDetailViewController {
   print("Yep")
} else {
  print ("Nope")
}
Steven Ossorio
Steven Ossorio
1,706 Points

Martin Wildfeuer Thank you for your reply. I added the code you've mentioned but get a new error now.

        override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "showPlaylistDetail" {
            if let playlistDetailController = segue.destinationViewController as? PlaylistDetailViewController {
                print("Yep")
            } else {
                print ("Nope")
            }
        }   
    }

The error I get is for if let playlistDetailController which is "Immutable value 'playlistDetailController' was never used; consider replacing it with '_' or remove it"

Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points

Sure, we don't really use "playlistDetailController" by now, so Xcode issues a warning. That does not prevent you from running the app, though. So let's give it a try and let me know what the console output is :)

Alam Castillo
PLUS
Alam Castillo
Courses Plus Student 505 Points
Alam Castillo
Alam Castillo
Courses Plus Student 505 Points

Have you found a solution for this yet? I am facing the same issue.

Steven Ossorio
Steven Ossorio
1,706 Points

None so far.

ian value
ian value
1,772 Points
ian value
ian value
1,772 Points

HI Alam,

Did you ever figure this out? I'm having the same issue.

boris said
boris said
3,607 Points
boris said
boris said
3,607 Points

I am also having the same issue. I tried using as! and it crashed. The breakpoint was on that line. Here is my code:

PlaylistMasterViewController

'''import UIKit

class PlaylistMasterViewController: UIViewController {

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "showPlaylistDetail" {
        let playlistDetailController = segue.destinationViewController as! PlaylistDetailViewController
         playlistDetailController.segueLabelText = "Something"
    }

}




@IBOutlet weak var aButton: UIButton!


override func viewDidLoad() {
    super.viewDidLoad()
    aButton.setTitle("Press Me!", forState: .Normal)
}

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

}

'''

PlaylistDetailViewController:

'''

// // PlaylistDetailViewController.swift // Algorhythm // // Created by Mac Owner on 2/29/16. // Copyright © 2016 Boris Said Developtment. All rights reserved. //

import UIKit

class PlaylistDetailViewController: UIViewController {

@IBOutlet weak var buttonPress: UILabel!
var segueLabelText: String = ""

override func viewDidLoad() {
    super.viewDidLoad()

    buttonPress.text = segueLabelText

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

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

}

'''

boris said
boris said
3,607 Points
boris said
boris said
3,607 Points

Actually, the error appears to be happening on line 17