Swiftui - Access UIKit methods/properties from UIViewRepresentable

Question

I have created a SwiftUI TextView based on a UITextView using UIViewRepresentable (s. code below). Displaying text in Swiftui works OK.

But now I need to access internal functions of UITextView from my model. How do I call e.g. UITextView.scrollRangeToVisible(_:) or access properties like UITextView.isEditable ?

My model needs to do these modifications based on internal model states.

Any ideas ? Thanks

(p.s. I am aware of TextEditor in SwiftUI, but I need support for iOS 13!)

struct TextView: UIViewRepresentable {
  @ObservedObject var config: ConfigModel = .shared
  @Binding var text: String
  
  @State var isEditable: Bool
  var borderColor: UIColor
  var borderWidth: CGFloat
  
  func makeCoordinator() -> Coordinator {
    Coordinator(self)
  }
  
  func makeUIView(context: Context) -> UITextView {
    let myTextView = UITextView()
    myTextView.delegate = context.coordinator
    
    myTextView.isScrollEnabled = true
    myTextView.isEditable = isEditable
    myTextView.isUserInteractionEnabled = true
    myTextView.layer.borderColor = borderColor.cgColor
    myTextView.layer.borderWidth = borderWidth
    myTextView.layer.cornerRadius = 8
    return myTextView
  }
  
  func updateUIView(_ uiView: UITextView, context: Context) {
    uiView.font = uiView.font?.withSize(CGFloat(config.textsize))
    uiView.text = text
  }
  
  class Coordinator : NSObject, UITextViewDelegate {
    
    var parent: TextView
    
    init(_ uiTextView: TextView) {
      self.parent = uiTextView
    }
    
    func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
      return true
    }
    
    func textViewDidChange(_ textView: UITextView) {
      self.parent.text = textView.text
    }
  }
}

I know this post, but my problem how to access UIKit functions during run time is not addressed there. — Chris
– Chris, Commented Dec 7, 2020 at 12:06

Asperi · Accepted Answer · 2020-12-07 12:07:50Z

You can use something like configurator callback pattern, like

struct TextView: UIViewRepresentable {
  @ObservedObject var config: ConfigModel = .shared
  @Binding var text: String
  
  @State var isEditable: Bool
  var borderColor: UIColor
  var borderWidth: CGFloat
  var configurator: ((UITextView) -> ())?     // << here !!

  func makeCoordinator() -> Coordinator {
    Coordinator(self)
  }
  
  func makeUIView(context: Context) -> UITextView {
    let myTextView = UITextView()
    myTextView.delegate = context.coordinator
    
    myTextView.isScrollEnabled = true
    myTextView.isEditable = isEditable
    myTextView.isUserInteractionEnabled = true
    myTextView.layer.borderColor = borderColor.cgColor
    myTextView.layer.borderWidth = borderWidth
    myTextView.layer.cornerRadius = 8
    return myTextView
  }

  func updateUIView(_ uiView: UITextView, context: Context) {
    uiView.font = uiView.font?.withSize(CGFloat(config.textsize))
    uiView.text = text

    // alternat is to call this function in makeUIView, which is called once,
    // and the store externally to send methods directly.
    configurator?(myTextView)                  // << here !!
  }

  // ... other code
}

and use it in your SwiftUI view like

TextView(...) { uiText in
   uiText.isEditing = some
}

Note: depending on your scenarios it might be additional conditions need to avoid update cycling, not sure.

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