如何在使用 CoreData 的 TextField 上使用 @Binding 可选？

Question

I have a CoreData entity called Counter , and I am wanting to make a view where the user has the ability to change some of the values. An element of the entity is sent to the EditCounterView inside the counter Binding variable. I want the user to able to edit the title of the element. However, I am having trouble trying to get the TextField binding to work properly. I get these two errors:

Cannot convert value of type 'Binding<String?>' to expected argument type 'Binding<String>'

Value of optional type 'FetchedResults<Counter>.Element?' (aka 'Optional<Counter>') must be unwrapped to refer to member 'title' of wrapped base type 'FetchedResults<Counter>.Element' (aka 'Counter')

With regards to the first error, I have no idea how I can fix this issue, as I have been trying to figure it out for a while. With regards to the second error, it suggests I either force unwrap or chain the optional. But when I do this, it gives me another error telling me to remove this.

My code is below:

struct EditCounterView: View {
    
    @Environment(\.managedObjectContext) var managedObjectContext
    @Environment(\.dismiss) var dismiss
    
    @Binding var editingCounter: Bool
    @Binding var counter: FetchedResults<Counter>.Element?

    var body: some View {
        NavigationView {
            VStack {
                CounterCellView(title: counter!.title!, icon: counter!.icon!, color: counter!.color!, date: counter!.date!)
                    .frame(maxWidth: .infinity, maxHeight: 80)
                    .padding()
                Form {
                    Section {
                        TextField("Required", text: $counter.title) // Where I am getting the error.
                    }
                }
            }
        }
    }
}

Answer 1

I reread your question. Here is my corrected answer. I changed your view a bit. I changed how counter was passed in to a simple let . Managed objects are classes conform to ObservableObject . You can pass them in as constants and still update their values.

I then took that value and made a custom binding that will take the value and then update the value. It is written presuming that counter.title is optional, but that counter itself is not.

struct EditCounterView: View {
    
    @Environment(\.managedObjectContext) var managedObjectContext
    @Environment(\.dismiss) var dismiss
    
    @Binding var editingCounter: Bool
    let counter: Counter

    var body: some View {
        NavigationView {
            VStack {
                CounterCellView(title: counter.title!, icon: counter.icon!, color: counter.color!, date: counter!.date!)
                    .frame(maxWidth: .infinity, maxHeight: 80)
                    .padding()
                Form {
                    Section {
                        // Custom Binding here...
                        TextField("Required", text: Binding<String>(
                            get: { counter.title ?? "" },
                            set: { newValue in
                                item.title = newValue
                            })
                        )
                    }
                }
            }
        }
    }
}