swiftui nsattributedstring uiviewcontrollerrepresentable

Custom UIViewController with UIViewcontrollerRepresentable that has a UITextView that crashes or is nil when called in SwiftUI

I have made a custom UIViewController called ViewControllerA and want to be able to use it so I made a UIViewControllerRepresentable called ViewControllerARepresentable as shown below, the problem though is that when I call ViewControllerARepresentable in my SwiftUI view and pass a value for stringToUpdateTextView, the ViewControllerA says the htmlTextView(UITextView) in ViewControllerA is nil and I'm not sure why.

ViewControllerARepresentable(stringToUpdateTextView: "<html>Send some Html Text as string here</html>")

ViewControllerARepresentable

public struct ViewControllerARepresentable: UIViewControllerRepresentable {
  var stringToUpdateTextView: String

  public func makeUIViewController(context: Context) -> ViewControllerA {
    let viewcontrollerA = ViewControllerA(testString: testingString)

    return viewcontrollerA
  }

  public func updateUIViewController(_ uiViewController: ViewControllerA, context: Context) {}
}

ViewControllerA

open class ViewControllerA: UIViewController {

  public var stringToUpdateTextView: String

  override open func viewDidLoad() {
    super.viewDidLoad()

htmlTextView.text = stringToUpdateTextView
  }

  @IBOutlet weak var htmlTextView: UITextView!

  public init(testString: String) {
    self.testString = testString
    super.init(nibName: nil, bundle: nil)
  }

  required public init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
}

Crash occurs at htmlTextView.text = stringToUpdateTextView saying that htmlTextView.text is nil even though its an IBOutlet. Any Change made to the htmlTextView like background color ,etc, also causes a crash if called in viewDidAppear or viewDidLoad

Solution

When instantiating your view controller in makeUIViewController, the outlets haven't been initialised yet.

The following code loads your view controller from the storyboard, and updates the properties in updateUIViewController:

ViewController.swift

import UIKit
import SwiftUI

class ViewController: UIViewController {

  @IBOutlet weak var htmlTextView: UITextView!

  override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
  }

}

struct ViewControllerWrapper: UIViewControllerRepresentable {
  typealias UIViewControllerType = ViewController

  @Binding var text: String

  func makeUIViewController(context: Context) -> ViewController {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    guard let viewController =  storyboard.instantiateViewController(
      identifier: "ViewController") as? ViewController else {
        fatalError("Cannot load from storyboard")
    }
    return viewController
  }

  func updateUIViewController(_ uiViewController: ViewController, context: Context) {
    uiViewController.htmlTextView.text = text
  }

}


struct ViewControllerPreview: PreviewProvider {
  static var previews: some View {
    ViewControllerWrapper(text: .constant("hello world!"))
  }
}

SwiftUIView.swift

struct SwiftUIView: View {
  @State var text = "Text"
  var body: some View {
    HStack {
      TextField("Text:", text: $text)
      ViewControllerWrapper(text: $text)
    }
  }
}