How do I get a textfield to display attributes of a core data entity? - swift

Question

I have a list of fruits. the struct FruitRowView provides the layout for the view of each row. In this FruitRowView, there's a TextField which I want to display the name of each fruit. I am having trouble doing this. The reason why I want to use a TextField to display the name of each fruit rather than a Text is so that users can easily edit the name of the fruit right from that TextField. In this case, fruits are the Core Data entity and the fruit name is an attribute of this entity.
Here is my core data class:
class CoreDataViewModel: ObservableObject {
let container: NSPersistentContainer
#Published var savedEntities: [FruitEntity] = []
init() {
container = NSPersistentContainer(name: "FruitsContainer")
container.loadPersistentStores { (description, error) in
if let error = error {
print("Error with coreData. \(error)")
}
}
fetchFruits()
}
func fetchFruits() {
let request = NSFetchRequest<FruitEntity>(entityName: "FruitEntity")
do {
savedEntities = try container.viewContext.fetch(request)
} catch let error {
print("Error fetching. \(error)")
}
}
func addFruit(text: String) {
let newFruit = FruitEntity(context: container.viewContext)
newFruit.name = text
saveData()
}
func saveData() {
do {
try container.viewContext.save()
fetchFruits()
} catch let error {
print("Error saving. \(error)")
}
}
}
Here is my contentView:
struct ContentView: View {
//sheet variable
#State var showSheet: Bool = false
#StateObject var vm = CoreDataViewModel()
#State var refresh: Bool
var body: some View {
NavigationView {
VStack(spacing: 20) {
Button(action: {
showSheet.toggle()
}, label: {
Text("Add Fruit")
})
List {
ForEach(vm.savedEntities) { fruit in
FruitRowView(vm: vm, fruit: fruit)
}
}
}
.navigationTitle("Fruits")
.sheet(isPresented: $showSheet, content: {
SecondScreen(refresh: $refresh, vm: vm)
})
}
}
}
Here is my popup screen (used to create a new fruit)
struct SecondScreen: View {
#Binding var refresh: Bool
#Environment(\.presentationMode) var presentationMode
#ObservedObject var vm: CoreDataViewModel
#State var textFieldText: String = ""
var body: some View {
TextField("Add fruit here...", text: $textFieldText)
.font(.headline)
.padding(.horizontal)
Button(action: {
guard !textFieldText.isEmpty else { return }
vm.addFruit(text: textFieldText)
textFieldText = ""
presentationMode.wrappedValue.dismiss()
refresh.toggle()
}, label: {
Text("Save")
})
}
}
Here is my FruitRowView:
struct FruitRowView: View {
//instance of core data model
#ObservedObject var vm: CoreDataViewModel
var fruit: FruitEntity
#State var fruitName = fruit.name
var body: some View {
TextField("Enter fruit name", text: $fruitName)
}
}
So the error that I'm getting is: 'Cannot use instance member 'fruit' within property initializer; property initializers run before 'self' is available'. This error occurs in the FruitRowView when I try to assign fruitName to fruit.name. I assume that there's an easy workaround for this but I haven't been able to figure it out.

Answer 1

Since the fruitEntities in the view model is a published property, you don't need a state variable in the row. You need the binding for the row view, and you should pass it in the content view.
You don't need to pass the view model to the row view as well.
struct FruitRowView: View {
// No need to pass view model to child, only pass the data
// #ObservedObject var vm: CoreDataViewModel
#Binding var fruitName: String
// You don't need this.
// #State var fruitName = fruit.name
var body: some View {
TextField("Enter fruit name", text: $fruitName)
}
}
struct ContentView: View {
...
List {
ForEach(vm.savedEntities) { fruit in
FruitRowView(fruitName: $fruit.name)
}
}
...
}