Updating SwiftUI view from Core Data non scalar attribute

Question

I have a Core Data NSManagedObject entity Person with a Bool attribute that I generate as a NSNumber. (the "Use Scalar Type" checkbox is not used, so the Bool attribute becomes an NSNumber) I am trying to observe this attribute, employed, to control the UI.

@ObservedObject var person: Person

var body: some View {
    List {
        Section {
            HStack {
                Toggle(isOn: $person.employed) { <-- 1
                    Text("Showing employed content..")
                }
            }
        }
        if person.employed.boolValue {
            Section { } etc

I get a warning at "1" saying: Cannot convert value of type 'Binding<NSNumber?>' to expected argument type 'Binding<Bool>' How can I make use of the employed attribute as a bool without changing it to a scalar?

Note: $person.employed.boolValue would not work it seems, and I would also have to account for the optional part.

Answer 1

One possible way to do it is via a custom Binding:

Toggle("Showing employed content..", isOn: Binding<Bool>(get: {
         person.employed?.boolValue == true
      }, set: { value in
         person.employed = NSNumber(value: value)
      }))  

Now, if you prefer this to be a computed property instead, you could do something like this:

var isEmployed: Binding<Bool> {
    Binding<Bool>(get: {
        person.employed?.boolValue == true
    }, set: { value in
        person.employed = NSNumber(value: value)
    })
}

var body: some View {
    Toggle("Showing employed content..", isOn: isEmployed)
}

Also, here is a possible implementation of an extension that handles optional NSNumber backed booleans (excuse my terible naming):

extension Binding where Value == NSNumber? {
    var boolBinding: Binding<Bool> {
        Binding<Bool>(get: {
            self.wrappedValue == true
        }, set: { value in
            self.wrappedValue = NSNumber(value: value)
        })
    }
}

which can be used like this:

Toggle("Showing employed content..", isOn: $person.employed.boolBinding)