SwiftUI UIViewRepresentable and Custom Delegate - swift

Question

When creating a UIViewControllerRepresentable for SwiftUI, how do you create a Coordinator so that it can access the delegate of a third party library?
In this case, I am trying to access BBMetal, a photo-filtering library.
This is a truncated version of the code we are trying to 'bridge' to SwiftUI:
class CameraPhotoFilterVC: UIViewController {
private var camera: BBMetalCamera!
private var metalView: BBMetalView!
private var faceView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
...
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
camera.start()
}...
}
extension CameraPhotoFilterVC: BBMetalCameraPhotoDelegate {
func camera(_ camera: BBMetalCamera, didOutput texture: MTLTexture) {
// do something with the photo
}
func camera(_ camera: BBMetalCamera, didFail error: Error) {
// In main thread
print("Fail taking photo. Error: \(error)")
}
}
Using UIViewRepresentable everything sets up properly and the CameraPhotoFilterVC works, starts up the camera, etc, but the extension does not respond. We tried to set this up as a Coordinator:
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIViewController(context: UIViewControllerRepresentableContext<CameraPreviewView>) -> CameraViewController {
let cameraViewController = CameraViewController()
// Throws an error because what we really want is a BBMetalCameraPhotoDelegate
//cameraViewController.delegate = context.coordinator
return cameraViewController
}
class Coordinator: NSObject, BBMetalCameraPhotoDelegate {
var parent: CameraPreviewView
init(_ parent: CameraPreviewView) {
self.parent = parent
}
func camera(_ camera: BBMetalCamera, didOutput texture: MTLTexture) {
print("do something with the photo")
}
func camera(_ camera: BBMetalCamera, didFail error: Error) {
print("Fail taking photo. Error: \(error)")
}
}
We also tried simply leaving an extension of the ViewController:
final class CameraViewController : UIViewController {
...
}
extension CameraViewController: BBMetalCameraPhotoDelegate {
func camera(_ camera: BBMetalCamera, didOutput texture: MTLTexture) {
...
}
However the delegate methods from BBMetalCameraPhotoDelegate do not 'fire.
I suppose the question is: in UIViewControllerRepresentable or UIViewRepresentable, how do you add an "external" delegate in the makeUIViewController method?
Usually, if this was say a UIPickerView, the following line would work:
picker.delegate = context.coordinator
But in this case the delegate is 'once removed'

Answer 1

You need to set the BBMetalCamera's delegate at some point before you use it.
You might do it immediately after creating it. You didn't show how you create it, so I don't know if that would be a good place to set it.
You could probably just do it in viewDidLoad:
override func viewDidLoad() {
super.viewDidLoad()
camera.photoDelegate = self
}