How to map a SwiftUI state to a binding of a different type

When working with states and bindings in SwiftUI, we sometimes might have a use case where we need to map a state type to a different binding type. Let's look at an example and see how to do that.

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Imagine, we have a SwiftUI view with a selection from a list and a button to save that selection. The button should be disabled as long as the user hasn't made a selection yet:

struct SaveView: View {

    @State private var selectedOption: SelectionOption?

    var body: some View {
        VStack {
            SelectionView(selectedOption: $selectedOption)
            Spacer()
            SaveButton(action: {}, isDisabled: ???)
        }
    }
}

The isDisabled parameter is of type Bindable<Bool> so we need some kind of mapping from the selectedOption state property. For that case, we can initialize a Binding as follows:

SaveButton(action: {}, isDisabled: Binding(
    get: { selectedOption == nil },
    set: { _ in }))

As shown above, we can create a custom binding using the Binding type which takes a get and a set closure. This is really useful when we need to add custom logic to a binding.

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