Creating a supplier and adding brands to them in SwiftUI with CoreData

Question

I'm building a inventory/patient management app for my store and although I managed to successfully create the patient part of it, the inventory part still eludes me. I need to create suppliers and link brands to them but I want to be able to create them with my app and not constantly code new suppliers and new brands. I managed to do that but with one glitch: every time I create a brand for a supplier, that same brand ends up in all the other suppliers created.(part of the naming attributes is in french) Here is the code for the supplier list:

import SwiftUI

struct FrameCompany: View {
   @Environment(\.managedObjectContext) var moc
   @FetchRequest(entity: FournisseursMontures.entity(), sortDescriptors: [NSSortDescriptor(keyPath: \FournisseursMontures.fournisseurs, ascending: true)])
   var Fournisseurs: FetchedResults<FournisseursMontures>
   
   @State private var showingAddScreen = false
   @State private var showingEditScreen = false
   
   var body: some View {
     
           List {
               ForEach(Fournisseurs, id: \.self) { Fournisseur in
                   NavigationLink(destination: Brand(Fournisseurs: Fournisseur)) {
                       VStack {
                           HStack {
                               Text(Fournisseur.fournisseurs ?? "")
                           }
                       }
                       
                   }
               }
               .onDelete(perform: deleteFournisseur)
           }
           .navigationBarTitle("Fournisseurs Montures")
           .navigationBarItems(leading: EditButton(), trailing:
                                   Button(action: {
                                       self.showingAddScreen.toggle()
                                   }) {
                                       Image(systemName: "plus")
                                   }
                               )
           .sheet(isPresented: $showingAddScreen) {
               AddNewCompany().environment(\.managedObjectContext, self.moc)
           }
           
       
   }
   func deleteFournisseur(at offsets: IndexSet) {
       for offset in offsets{
           let Fournisseur = Fournisseurs[offset]
           moc.delete(Fournisseur)
       }
       try? moc.save()
       
   }
}

struct FrameCompany_Previews: PreviewProvider {
   static var previews: some View {
       FrameCompany()
   }
}

Here is the code for adding a company:

import SwiftUI

struct AddNewCompany: View {
   @Environment(\.managedObjectContext) var moc
   @Environment(\.presentationMode) var presentationMode
   
   @State private var fournisseurs = ""
   
   var body: some View {
       Form {
           Section {
               TextField("Fournisseur", text: $fournisseurs)
           }
           Section{
               Button("Enregistrer") {
                   let newCompany = FournisseursMontures(context: self.moc)
                   newCompany.fournisseurs = self.fournisseurs
                   
                   try? self.moc.save()
                   self.presentationMode.wrappedValue.dismiss()
               }
           }
       }
   }
}

struct AddNewCompany_Previews: PreviewProvider {
   static var previews: some View {
       AddNewCompany()
   }
}

here is the code for brand list:

//
//  Brand.swift
//  PIBAv1
//
//  Created by Hicham on 2020-11-19.
//  Copyright © 2020 Hicham. All rights reserved.
//

import SwiftUI

struct Brand: View {
    @Environment(\.managedObjectContext) var moc
    @FetchRequest(entity: Collections.entity(), sortDescriptors: [
            NSSortDescriptor(keyPath: \Collections.marques, ascending: true)])
    var Brands: FetchedResults<Collections>
    
    @State private var showingAddScreen = false
    @State private var showingEditScreen = false
    
    @ObservedObject var Fournisseurs: FournisseursMontures
    var body: some View {
                    List {
                ForEach(Brands, id: \.self) {Brand in
                    NavigationLink(destination: Model(Brands: Brand)) {
                        VStack {
                            HStack {
                                Text(Brand.marques ?? "")
                            }
                        }
                }
            }
                .onDelete(perform: deleteBrand)
        }
            .navigationBarTitle("Marques")
            .navigationBarItems(leading: EditButton(), trailing:
                                    Button(action: {
                                        self.showingAddScreen.toggle()
                                    }) {
                                        Image(systemName: "plus")
                                    }
            )
            .sheet(isPresented: $showingAddScreen) {
                AddNewBrand().environment(\.managedObjectContext, self.moc)
                
            }
    
}
    func deleteBrand(at offsets: IndexSet) {
        for offset in offsets{
            let Brand = Brands[offset]
            moc.delete(Brand)
        }
        try? moc.save()
    }

struct Brand_Previews: PreviewProvider {
    static var previews: some View {
        Brand(Fournisseurs: FournisseursMontures())
    }
}
}

and finally the code for adding a new brand:

import SwiftUI

struct AddNewBrand: View {
    @Environment(\.managedObjectContext) var moc
    @Environment(\.presentationMode) var presentationMode
    
    @State private var marques = ""
    
    var body: some View {
        Form {
            Section {
                TextField("Marques", text: $marques)
            }
            Section{
                Button("Enregistrer") {
                    let newBrand = Collections(context: self.moc)
                    newBrand.marques = self.marques
                    
                    try? self.moc.save()
                    self.presentationMode.wrappedValue.dismiss()
                }
            }
        }
    }
}

struct AddNewBrand_Previews: PreviewProvider {
    static var previews: some View {
        AddNewBrand()
    }
}

Thanks for the help!

Answer 1

It sounds more like a database issue vs a code issue. Your table relationships would probably be more helpful.

From what I understand a Brand is assigned to multiple Suppliers but it should be that a Supplier should have multiple (Exclusive) Brands.

The relationship from Brand to Supplier should be one to one but it is one to many.