SwiftUI MVVM 已发布 var 未在不同视图之间更新

Question

I have the View 1 and View 2, View 1 has a button that navigate to View 2, in View 2 there is list of options to choose when clicked is expected to update a variable in View 1, but the variable in View 1 does not get updated.

View1.swift

struct View1: View {
    @ObservedObject var viewModel = MyViewModel()
    
    var body: some View {
        NavigationLink(destination: View2()) {
            VStack {
                Text(self.viewModel.addressChosen)
            }
        }
    }
}

View2.swift

struct View2: View {
    @ObservedObject var viewModel = MyViewModel()

    var body: some View {
        Button(action: {
            self.viewModel.chooseAddress(addressSelected: "Chosen Address")
        }) {
            VStack {
                Text(self.viewModel.addressChosen)
            }
        }
    }
}

MyViewModel.swift

class MyViewModel: ObservableObject, ModelService {
    @Published var addressChosen = "Default"

    func chooseAddress(addressSelected: String) {
        print(addressSelected)
        self.addressChosen = addressSelected
    }
}

The var addressChosen is updated in View 2, but when I go back to View 1, the variable does not get updated. What am I doing wrong? Thank you.

Answer 1

You are using two different MyViewModel . You need to pass the same MyViewModel() or only addressChosen from View1 to View2 .

Pass the same MyViewModel() to View2

struct View1: View {
    @ObservedObject var viewModel = CartViewModel()
    
    var body: some View {
        NavigationLink(destination: View2(viewModel: viewModel)) {
            VStack {
                Text(self.viewModel.addressChosen)
            }
        }
    }
}

struct View2: View {
    @ObservedObject var viewModel: CartViewModel

    var body: some View {
        Button(action: {
            self.viewModel.chooseAddress(addressSelected: "Chosen Address")
        }) {
            VStack {
                Text(self.viewModel.addressChosen)
            }
        }
    }
}

class CartViewModel: ObservableObject {
    @Published var addressChosen = "Default"

    func chooseAddress(addressSelected: String) {
        print(addressSelected)
        self.addressChosen = addressSelected
    }
}

Pass addressChosen to View2

struct View1: View {
    @ObservedObject var viewModel = CartViewModel()
    
    var body: some View {
        NavigationLink(destination: View2(addressChosen: $viewModel.addressChosen)) {
            VStack {
                Text(self.viewModel.addressChosen)
            }
        }
    }
}

struct View2: View {
    @Binding var addressChosen: String

    var body: some View {
        Button(action: {
            self.addressChosen =  "Chosen Address"
        }) {
            VStack {
                Text(self.addressChosen)
            }
        }
    }
}

class CartViewModel: ObservableObject {
    @Published var addressChosen = "Default"

    func chooseAddress(addressSelected: String) {
        print(addressSelected)
        self.addressChosen = addressSelected
    }
}