Swift + Xcode : Preview not working. Xcode error

Using Swift
1

Hello,
I am writing a Swift program and am trying to get one of the previews to work but with no luck. The error message I get is: Program crashed due to missing environment of type NavigationViewModel. To resolve add .envionmentObject(NavigationViewModel(...)) to the appropriate preview. I have tried several things with no luck. If anyone could point out my error it would be appreciated. Below is my code. The preview section is at the bottom. BTW, I am having trouble figuring out how to get the code in a code fence so I apologize for that. It is clearly just one of those days.
Regards
Chris

import SwiftUI
struct ListView: View {
@EnvironmentObject var navVM: NavigationViewModel
var body: some View {
Spacer().frame(height: 30)
VStack {
ForEach (navVM.options, id: .self) { option in
switch option.id {
case 0:
HomeItem(imageName: option.imageName, title: option.title, id: option.id)
case 1, 4, 7:
MainItem(imageName: option.imageName, title: option.title, id: option.id)
case 2, 3, 5, 6, 8, 9:
SubItem(title: option.title, id: option.id)
default:
Text("Something went wrong")
} // end switch
} // end for each
} // end vstack
Spacer()
.frame(width: 180, alignment: .leading)
} // end var body
} // end list view
struct HomeItem: View {
let imageName : String
let title : String
let id: Int
// let currentViewId: Int
@EnvironmentObject var navVM: NavigationViewModel
var body: some View {
HStack{
Image(systemName: imageName)
.resizable()
.aspectRatio(contentMode: .fit)
.frame(width: 30, height: 30, alignment: .leading)
.foregroundColor(navVM.highLightedImage == id ? Color.blue : Color.black)
.padding(.leading, 20 )
.padding(.top, 10)
Text(title)
.font(.system(size: 15))
.underline()
.frame(width: 125, alignment: .leading)
.foregroundColor(Color.blue)
.padding(.top, 15)
.onTapGesture {
navVM.updateCurrentViewId(value: id)
navVM.updateSelectedItem(value: 0)
navVM.updateHighLightedImage(value: 0)
}
} // end hstack
}
}
struct MainItem: View {
let imageName : String
let title : String
let id: Int
@EnvironmentObject var navVM: NavigationViewModel
var body: some View {
HStack{
Image(systemName: imageName)
.resizable()
.aspectRatio(contentMode: .fit)
.frame(width: 30, height: 30, alignment: .leading)
.foregroundColor(navVM.highLightedImage == id ? Color.blue : Color.black)
.padding(.leading, 20 )
.padding(.top, 10)
Text(title)
.font(.system(size: 15))
.frame(width: 125, alignment: .leading)
.padding(.top, 10)
} // end hstack
}
}
struct SubItem: View {
let title: String
// let currentViewId : Int
let id: Int
@EnvironmentObject var navVM: NavigationViewModel
var body: some View {
HStack{
Text(title)
.font(.system(size: 13))
.underline()
.frame(width: 35, alignment: .leading)
.foregroundColor(Color.blue)
.padding(.bottom, 2)
.padding(.leading, 15)
.onTapGesture {
navVM.updateCurrentViewId(value: id)
navVM.updateSelectedItem(value: id)
switch navVM.selecteditem {
case 2, 3:
navVM.updateHighLightedImage(value: 1)
case 5, 6:
navVM.updateHighLightedImage(value: 4)
case 8, 9:
navVM.updateHighLightedImage(value: 7)
default:
navVM.updateHighLightedImage(value: 0)
}
}
switch navVM.currentViewId {
case id:
Image(systemName: "checkmark").padding(.bottom, 5).foregroundColor(Color.blue).opacity(100)
default:
Image(systemName: "checkmark").padding(.bottom, 5).foregroundColor(Color.blue).opacity(0)
}
} // end hstack
}
}
struct ListView_Previews: PreviewProvider {
@EnvironmentObject var navVM: NavigationViewModel
static var previews: some View {
ListView()
}
// .environmentObject(navVM: NavigationViewModel())
}

2

BTW, I am having trouble figuring out how to get the code in a code fence so I apologize for that.

See this guide about how to use code fences.

Here's what you need to do in order to use an environment object in your preview:

struct ListView_Previews: PreviewProvider {

    @StateObject static var navVM = NavigationViewModel()

    static var previews: some View {
        ListView()
            .environmentObject(navVM)
    }

}
3

Thanks Peter. Did not know to use ``` around the code. Will use them from now on.
I ended up using the code below.

struct ListView_Previews: PreviewProvider {
    static var previews: some View {
        ListView().environmentObject(NavigationViewModel())
    }
}