How Do I Add UIViewController to UIScrollView in Swift

Question

I want to have a UIScrollView of UIViewControllers. I tested the ScrollView and it works fine, except when I try to add the ViewControllers. The project builds fine, but I get a "fatal error: unexpectedly found nil while unwrapping an Optional value" error that points at the ViewController, particularly the line:

self.imageView.image = UIImage(named: self.image!)

However, when I inspect the object, I can see variables image and text have values in the ViewController. I'm using Xcode 6.3 Beta and building to iOS8.1 target.

Here's the code:

import UIKit

class ViewController: UIViewController {

//@IBOutlet weak var contentScrollView: UIScrollView!

@IBOutlet var contentScrollView: UIScrollView!

//test to make sure ScrollView functions
//let colors = [UIColor.redColor(),UIColor.blueColor(), UIColor.greenColor(), UIColor.whiteColor(), UIColor.blackColor(), UIColor.yellowColor()]

var frame = CGRectMake(0, 0, 0, 0)

var dataArray = [PostItem]()

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

    var da = PostItem(text: "test 1", pic: "beans.jpg")
    self.dataArray.append(da!)

    da = PostItem(text: "test 2", pic: "coffee.jpg")
    self.dataArray.append(da!)

    da = PostItem(text: "test 3", pic: "coffeeCup.jpg")
    self.dataArray.append(da!)

    for index in 0..<self.dataArray.count{
        self.frame.origin.y = self.contentScrollView.frame.size.height * CGFloat(index)
        self.frame.size = self.contentScrollView.frame.size
        self.contentScrollView.pagingEnabled = false
        let tempPost = self.dataArray[index]


        var vc = PostViewController()
        vc.text = tempPost.postText
        vc.image = tempPost.postImage

        self.contentScrollView.addSubview(vc.view)

    }

    self.contentScrollView.contentSize = CGSizeMake(self.view.frame.size.width, CGFloat(self.dataArray.count) * self.contentScrollView.frame.height)
}

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

And here is the code for the ViewController I want to add:

import UIKit

class PostViewController: UIViewController {

    //let postItem
    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var postToFBButton: UIButton!
    @IBOutlet weak var postToTwitterButton: UIButton!
    @IBOutlet weak var postText: UILabel!

    var image:String?
    var text:String?

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        self.imageView.image = UIImage(named: self.image!)
        self.postText.text = text!
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()

        // Dispose of any resources that can be recreated.

    }}

maybe UIImage() returned nil – nielsbot Feb 14 '15 at 16:06 — nielsbot, Feb 14 '15 at 16:06

gabbler · Answer 1 · 2015-02-14T16:23:19.880

0

The fix is to create the PostViewController through instantiateViewControllerWithIdentifier from storyboard, this way, it will have an imageView loaded from storyboard when its view is added to the scrollview.

edited Feb 14 '15 at 16:23

answered Feb 14 '15 at 15:51

gabbler

13,626
4
32
44

thanks for the quick response. The change didn't work... Added PostViewController as a child of the parent view as `self.addChildViewController(vc)` still getting the error... – Tony Armstrong Feb 14 '15 at 16:02
2

Please create the PostViewController from storyboard with a storyboard ID, it seems you don't have an imageView. – gabbler Feb 14 '15 at 16:10
OK. Problem is, I created a separate XIB for `PostViewController`. Is there an equivalent method to `instantiateViewControllerWithIdentifier` that I can use to instantiate from the XIB I created? – Tony Armstrong Feb 14 '15 at 17:01
2

You can use `initWithNibName`. – gabbler Feb 14 '15 at 17:03
using `iniitWithNibName` worked. Thanks! I assume I need to add each ViewController that I want to place, individually, as the array of VCs I created isn't being displayed. Is that correct? – Tony Armstrong Feb 14 '15 at 21:22
Yes, you should do addChildViewController, see http://stackoverflow.com/a/17332864/4016786, it gives you more control on the view that is added. – gabbler Feb 15 '15 at 01:49

How Do I Add UIViewController to UIScrollView in Swift

1 Answers1