Access #Environment object from UIViewControllerRepresentable object - swiftui

Question

I used this approach to incorporate camera with swiftUI:
https://medium.com/#gaspard.rosay/create-a-camera-app-with-swiftui-60876fcb9118
The UIViewControllerRepresentable is implemented by PageFourView class. PageFourView is one of the TabView of the parental View. I have an #EnvironmentObject passed from the SceneDelegate to the parent view and then to PageFourView. But when I am trying to acess #EnvironmentObject from makeUIViewController method of PageFourView I get an error:
Fatal error: No ObservableObject of type Data found. A
View.environmentObject(_:) for Data may be missing as an ancestor of
this view
... even though I can see the #Environment object from context.environment. Here is my code:
import UIKit
import SwiftUI
import Combine
final class PageFourView: UIViewController, UIViewControllerRepresentable {
public typealias UIViewControllerType = PageFourView
#EnvironmentObject var data: Data
var previewView: UIView!
override func viewDidLoad() {
previewView = UIView(frame: CGRect(x:0, y:0, width: UIScreen.main.bounds.size.width, height: UIScreen.main.bounds.size.height))
previewView.contentMode = UIView.ContentMode.scaleAspectFit
view.addSubview(previewView)
}
func makeUIViewController(context: UIViewControllerRepresentableContext<PageFourView>) -> PageFourView {
print(context.environment)
print(self.data.Name)
return PageFourView()
}
func updateUIViewController(_ uiViewController: PageFourView, context: UIViewControllerRepresentableContext<PageFourView>) {
}
}
struct PageFourView_Previews: PreviewProvider {
#State static var data = Data()
static var previews: some View {
PageFourView().environmentObject(self.data)
}
}
here is the parental view that PageFourView is called from:
import SwiftUI
struct AppView: View {
#EnvironmentObject var data: Data
var body: some View {
TabView {
PageOneView().environmentObject(data)
.tabItem {
Text("PageOne")
}
PageTwoView().environmentObject(data)
.tabItem {
Text("PageTwo")
}
PageThreeView().environmentObject(data)
.tabItem {
Text("PageThree")
}
PageFourView().environmentObject(data)
.tabItem {
Text("PageFour")
}
}
}
}
struct AppView_Previews: PreviewProvider {
#State static var data = Data()
static var previews: some View {
AppView().environmentObject(self.data)
}
}
final class CameraViewController: UIViewController {
let cameraController = CameraController()
var previewView: UIView!
override func viewDidLoad() {
previewView = UIView(frame: CGRect(x:0, y:0, width: UIScreen.main.bounds.size.width, height: UIScreen.main.bounds.size.height))
previewView.contentMode = UIView.ContentMode.scaleAspectFit
view.addSubview(previewView)
cameraController.prepare {(error) in
if let error = error {
print(error)
}
try? self.cameraController.displayPreview(on: self.previewView)
}
}
}
extension CameraViewController : UIViewControllerRepresentable{
public typealias UIViewControllerType = CameraViewController
public func makeUIViewController(context: UIViewControllerRepresentableContext<CameraViewController>) -> CameraViewController {
return CameraViewController()
}
public func updateUIViewController(_ uiViewController: CameraViewController, context: UIViewControllerRepresentableContext<CameraViewController>) {
}
}

Answer 1

And UIViewRepresentable and UIViewControllerRepresentable is-a View and must be a struct.
In described case controller representable is not needed, because you operate with view, so here is corrected code:
struct PageFourView: UIViewRepresentable {
#EnvironmentObject var data: Data
func makeUIView(context: Context) -> UIView {
let view = UIView(frame: CGRect(x:0, y:0, width: UIScreen.main.bounds.size.width,
height: UIScreen.main.bounds.size.height))
view.contentMode = UIView.ContentMode.scaleAspectFit
print(context.environment)
print(self.data.Name)
return view
}
func updateUIView(_ uiView: UIView, context: Context) {
}
}
btw, you don't need to pass .environmentObject to subviews in same view hierarchy, only for new hierarchy, like sheets, so you can use simplified code as below
var body: some View {
TabView {
PageOneView()
.tabItem {
Text("PageOne")
}
PageTwoView()
.tabItem {
Text("PageTwo")
}
PageThreeView()
.tabItem {
Text("PageThree")
}
PageFourView()
.tabItem {
Text("PageFour")
}
}
}
Update: for CameraViewController just wrap it as below
struct CameraView: UIViewControllerRepresentable {
func makeUIViewController(context: Context) -> CameraViewController {
CameraViewController()
}
func updateUIViewController(_ uiViewController: CameraViewController, context: Context) {
}
}