SwiftUI Observed Object not updating - swiftui

Question

Really just starting out with SwiftUI and trying to get my head around MVVM.
The code below displays a height and 4 toggle buttons, thus far I have only connected 2.
Major up and Major Down.
When clicked I see in the console that the value is altered as expected.
What I don't see is the the main display updating to reflect the change.
I have tried refactoring my code to include the view model into each Struct but still not seeing the change.
I think I have covered the basics but am stumped, I'm using a single file for now but plan to move the Model and ViewModel into separate files when I have a working mockup.
Thanks for looking.
import SwiftUI
/// This is our "ViewModel"
class setHeightViewModel: ObservableObject {
struct ImperialAndMetric {
var feet = 16
var inches = 3
var meters = 4
var CM = 95
var isMetric = true
}
// The model should be Private?
// ToDo: Fix the private issue.
#Published var model = ImperialAndMetric()
// Our getters for the model
var feet: Int { return model.feet }
var inches: Int { return model.inches }
var meters: Int { return model.meters }
var cm: Int { return model.CM }
var isMetric: Bool { return model.isMetric }
/// Depending upon the selected mode, move the major unit up by one.
func majorUp() {
if isMetric == true {
model.meters += 1
print("Meters is now: \(meters)")
} else {
model.feet += 1
print("Feet is now: \(feet)")
}
}
/// Depending upon the selected mode, move the major unit down by one.
func majorDown() {
if isMetric == true {
model.meters -= 1
print("Meters is now: \(meters)")
} else {
model.feet -= 1
print("Feet is now: \(feet)")
}
}
/// Toggle the state of the display mode.
func toggleMode() {
model.isMetric = !isMetric
}
}
// This is our View
struct ViewSetHeight: View {
// UI will watch for changes for setHeihtVM now.
#ObservedObject var setHeightVM = setHeightViewModel()
var body: some View {
NavigationView {
Form {
ModeArea(viewModel: setHeightVM)
SelectionUp(viewModel: setHeightVM)
// Show the correct height format
if self.setHeightVM.isMetric == true {
ValueRowMetric(viewModel: self.setHeightVM)
} else {
ValueRowImperial(viewModel: self.setHeightVM)
}
SelectionDown(viewModel: setHeightVM)
}.navigationTitle("Set the height")
}
}
}
struct ModeArea: View {
var viewModel: setHeightViewModel
var body: some View {
Section {
if viewModel.isMetric == true {
SwitchImperial(viewModel: viewModel)
} else {
SwitchMetric(viewModel: viewModel)
}
}
}
}
struct SwitchImperial: View {
var viewModel: setHeightViewModel
var body: some View {
HStack {
Button(action: {
print("Imperial Tapped")
}, label: {
Text("Imperial").onTapGesture {
viewModel.toggleMode()
}
})
Spacer()
Text("\(viewModel.feet)\'-\(viewModel.inches)\"").foregroundColor(.gray)
}
}
}
struct SwitchMetric: View {
var viewModel: setHeightViewModel
var body: some View {
HStack {
Button(action: {
print("Metric Tapped")
}, label: {
Text("Metric").onTapGesture {
viewModel.toggleMode()
}
})
Spacer()
Text("\(viewModel.meters).\(viewModel.cm) m").foregroundColor(.gray)
}
}
}
struct SelectionUp: View {
var viewModel: setHeightViewModel
var body: some View {
Section {
HStack {
Button(action: {
print("Major Up Tapped")
viewModel.majorUp()
}, label: {
Image(systemName: "chevron.up").padding()
})
Spacer()
Button(action: {
print("Minor Up Tapped")
}, label: {
Image(systemName: "chevron.up").padding()
})
}
}
}
}
struct ValueRowImperial: View {
var viewModel: setHeightViewModel
var body: some View {
HStack {
Spacer()
Text(String(viewModel.feet)).accessibility(label: Text("Feet"))
Text("\'").foregroundColor(Color.gray).padding(.horizontal, -10.0).padding(.top, -15.0)
Text("-").foregroundColor(Color.gray).padding(.horizontal, -10.0)
Text(String(viewModel.inches)).accessibility(label: Text("Inches"))
Text("\"").foregroundColor(Color.gray).padding(.horizontal, -10.0).padding(.top, -15.0)
Spacer()
}.font(.largeTitle).padding(.zero)
}
}
struct ValueRowMetric: View {
var viewModel: setHeightViewModel
var body: some View {
HStack {
Spacer()
Text(String(viewModel.meters)).accessibility(label: Text("Meter"))
Text(".").padding(.horizontal, -5.0).padding(.top, -15.0)
Text(String(viewModel.cm)).accessibility(label: Text("CM"))
Text("m").padding(.horizontal, -5.0).padding(.top, -15.0).font(.body)
Spacer()
}.font(.largeTitle)
}
}
struct SelectionDown: View {
var viewModel: setHeightViewModel
var body: some View {
Section {
HStack {
Button(action: {
print("Major Down Tapped")
viewModel.majorDown()
}, label: {
Image(systemName: "chevron.down").padding()
})
Spacer()
Button(action: {
print("Minor Down Tapped")
}, label: {
Image(systemName: "chevron.down").padding()
})
}
}
}
}

Answer 1

At the moment you receive the setHeightViewModel in various views as a var,
you should receive it as an ObservedObject.
I suggest you try this, in ViewSetHeight
#StateObject var setHeightVM = setHeightViewModel()
and in all your other views where you pass this model, use:
#ObservedObject var viewModel: setHeightViewModel
such as in ModeArea, SwitchImperial, SwitchMetric, SelectionUp, etc...
Alternatively you could use #EnvironmentObject ... to pass the setHeightViewModel
to all views that needs it.