Getting nil when calling a wrapped UIViewController's function in a SwiftUI class - swift

Question

So below is a simple picture taking ViewController that I have
final class TakePhotoViewController : UIViewController, AVCapturePhotoCaptureDelegate {
var captureSession : AVCaptureSession!
var cameraOutput : AVCapturePhotoOutput!
var previewLayer : AVCaptureVideoPreviewLayer!
let device = AVCaptureDevice.default(for: .video)!
override func viewDidLoad(){
print("viewDidLoad")
setupCameraLayouts()
}
private func setupCameraLayouts(){
print("setupCameraLayouts")
captureSession = AVCaptureSession()
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
captureSession.sessionPreset = AVCaptureSession.Preset.hd1920x1080
cameraOutput = AVCapturePhotoOutput()
previewLayer.frame = CGRect(x: view.frame.origin.x, y: view.frame.origin.y+view.frame.height/13, width: view.frame.width, height: view.frame.height/1.2475)
do {
try device.lockForConfiguration()
} catch {
return
}
device.focusMode = .continuousAutoFocus
device.unlockForConfiguration()
}
private func startCamera(){
print("startCamera")
if let input = try? AVCaptureDeviceInput(device: device) {
if captureSession.canAddInput(input) {
captureSession.addInput(input)
if captureSession.canAddOutput(cameraOutput){
captureSession.addOutput(cameraOutput)
view.layer.addSublayer(previewLayer)
captureSession.startRunning()
} else {
print("else in : captureSession.canAddOutput(cameraOutput)")
}
} else {
print("else in : captureSession.canAddInput(input)")
}
} else {
print("else in : input = try? AVCaptureDeviceInput(device: device)")
}
}
func cameraPressed(){
print("cameraPressed")
let settings = AVCapturePhotoSettings()
let previewPixelType = settings.availablePreviewPhotoPixelFormatTypes.first!
let previewFormat = [
kCVPixelBufferPixelFormatTypeKey as String: previewPixelType,
kCVPixelBufferWidthKey as String: 160,
kCVPixelBufferHeightKey as String: 160
]
settings.previewPhotoFormat = previewFormat
cameraOutput.capturePhoto(with: settings, delegate: self)
}
func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?){
print("photoOutput")
captureSession.stopRunning()
print("Got something")
}
}
extension TakePhotoViewController : UIViewControllerRepresentable {
public typealias UIViewControllerType = TakePhotoViewController
func makeUIViewController(context: UIViewControllerRepresentableContext<TakePhotoViewController>) -> TakePhotoViewController {
print("makeUIViewController")
return TakePhotoViewController()
}
func updateUIViewController(_ uiViewController: TakePhotoViewController, context: UIViewControllerRepresentableContext<TakePhotoViewController>) {
print("updateUIViewController")
}
}
As you can see, I have it "wrapped" using UIViewControllerRepresentable so I can use it in SwiftUI View. Unless there's better ways to do this, I found that this was the only way to do it.
Below is the SwiftUI class where i'm calling this.
struct ContentView: View {
let TPVC = TakePhotoViewController()
var body: some View {
VStack {
TPVC.startCamera()
Button(action: {
self.TPVC.cameraPressed()
}) {
Text("Hello World")
.fontWeight(.bold)
.font(.title)
.padding()
.background(Color.purple)
.cornerRadius(40)
.foregroundColor(.white)
.padding(10)
.overlay(
RoundedRectangle(cornerRadius: 40)
.stroke(Color.purple, lineWidth: 5)
)
}
}
}
}
So I know (from the print statements) that the the TakePhotoVC is being called and the nil error variables (and, really, all variables) aren't nil.
That being said, when the error happens (which is when I click the button), the various variables (captureSession, CaptureOutput) are nil which causes obvious errors. In the ContentView I create a variable for the class instance so I can reference to it whenever but it seems that if you call it again it creates a whole new class reference/instance

Answer 1

Your ContentView is a struct, ie. value, it is recreated on each UI refresh, so your TPVC also recreated.
Moreover UIViewControllerRepresentable expected to be some View to be used in ViewBuilder. So it is mis-concept in your code.
The tutorial Interfacing with UIKit should help you.