Model

I have different variables in Travel.

import Foundation

struct Travel: Identifiable, Codable {
    var id = UUID()
    var name: String
    var date = Date()
    var location: String
    var isFav: Bool
    var score: Float
    var comment: String
}

View model

I load and save data with UserDefaults. Always its work but in this model not.

import Foundation


class TravelViewModel: ObservableObject {
    @Published var travelList = [Travel] ()
    @Published var travelled = 0
    
    init(){
        load()
    }
    
    func load() {
        guard let data = UserDefaults.standard.data(forKey: "travelList"),
              let savedTravels = try? JSONDecoder().decode([Travel].self, from: data) else { travelList = []; return }
        
        travelList = savedTravels
    }
    
    func save() {
        do {
            let data = try JSONEncoder().encode(travelList)
            UserDefaults.standard.set(data, forKey: "travelList")
        } catch {
            print(error)
        }
    }
    
}

Adding Item View

I have addItems func and use this func in addItem button.

import SwiftUI

struct AddTravelView: View {
    
    @StateObject var VM = TravelViewModel()
    
    @State var name = ""
    @State var location = ""
    @State var isFav = false
    @State var score = 0.00
    @State var comment = ""
    
    var body: some View {
        VStack {
            ZStack {
                Rectangle()
                    .fill(.black.opacity(0.2))
                    .cornerRadius(20)
                    .frame(width: 350, height: 350)
                VStack{
                    HStack {
                        Text("Name:")
                            .font(.system(size: 16 , weight: .medium))
                        TextField("Type..", text: $name)
                    }
                    HStack {
                        Text("Location:")
                            .font(.system(size: 16 , weight: .medium))
                        TextField("Type..", text: $location)
                    }
                    HStack {
                        Text("Score: \(Int(score))")
                            .font(.system(size: 16 , weight: .medium))
                        Slider(value: $score, in: 0...10, step: 1)
                    }
                    Spacer()
                    
                    ZStack(alignment: .topLeading) {
                        Rectangle()
                            .fill(.white)
                            .cornerRadius(20)
                            .frame(height: 200)
                        VStack(alignment: .leading) {
                            TextField("Comment...", text: $comment, axis: .vertical)
                        }.padding()
                    }
                }
                .padding()
                .frame(width: 300, height: 200)
            }
            
            Button {
                addTravel()
            } label: {
                ZStack{
                    Rectangle()
                        .fill(.black.opacity(0.2))
                        .cornerRadius(20)
                        .frame(width: 350 , height: 100)
                        
                    
                    Text("ADD TRAVEL")
                        .font(.system(size: 25, weight: .medium, design: .monospaced))
                        .foregroundColor(.black)
                }.padding()
            }

            
        }
    }
    
    func addTravel(){
        VM.travelList.append(Travel(name: name, location: location, isFav: isFav, score: Float(score), comment: comment))
    }
    
}

struct AddTravelView_Previews: PreviewProvider {
    static var previews: some View {
        AddTravelView()
    }
}

Recent Adds view

In this page i wanna see Items i add before

import SwiftUI

struct RecentTravels: View {
    
    @StateObject var VM = TravelViewModel()
    
    var body: some View {
        VStack {
            ForEach(VM.travelList) {Travel in
                HStack{
                    Image(systemName: "questionmark")
                        .frame(width: 50, height: 50)
                        .padding()
                        .overlay {
                            RoundedRectangle(cornerRadius: 5)
                                .stroke(.black, lineWidth: 2)
                        }
                    VStack(alignment: .leading) {
                        Text(Travel.name)
                            .font(.subheadline)
                            .bold()
                            .lineLimit(1)
                        Text("\(Travel.date)")
                            .font(.footnote)
                            .opacity(0.9)
                            .lineLimit(1)
                    }
                    
                    Spacer()
                    VStack {
                        Image(systemName: "heart")
                        Spacer()
                        Text("\(Travel.score)")
                    }
                    .frame(height: 50)
                    .font(.system(size: 22))
                    
                }
            }
        }
    }
}

struct RecentTravels_Previews: PreviewProvider {
    static var previews: some View {
        RecentTravels()
    }
}

And ContentView

and calling those 2 views in ContentView.

import SwiftUI

struct ContentView: View {
    
    @StateObject var VM = TravelViewModel()
    
    var body: some View {
        VStack {
            
            AddTravelView()
            
            RecentTravels()
        }
        .padding()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

When i write the all code in only ContentView is work but when i call another pages its not work. Usually it was work when i presss add item button and restart app but now its nothing. Its not work even restart the app.

CodePudding user response：

The problem you have is that you have multiple VM, that have no relations to each other. You must not have more than one source of truth in @StateObject var VM = TravelViewModel().

Keep the one you have in ContentView, and pass it to the other view like this: VStack {....}.environmentObject(VM).

In your AddTravelView and RecentTravels , add @EnvironmentObject var VM: TravelViewModel instead of @StateObject var VM = TravelViewModel().

Have a look at this link, it gives you some good examples of how to manage data in your app:
https://developer.apple.com/documentation/swiftui/managing-model-data-in-your-app