Binding for @dynamicMemberLookup members

[piterwilson]

Hi @kylehickinson

I need to be able to pass the members created using @dynamicMemberLookup such as title, url and the rest as a Binding.

I wanted to extract away the logic for a custom View that reacts to title (for example).

I found myself doing this because passing the member directly did not cause the custom View to update:

extension WebViewStore {
    // Creates a `Binding` for any member created using @dynamicMemberLookup
    func binding<Value>(for keyPath: KeyPath<WebViewStore, Value>) -> Binding<Value> {
        Binding(get: { self[keyPath: keyPath] }, set: {_ in })
    }
}

...

struct BrowserTitleBarView: View {
    @Binding var title: String?
    var body: some View {
        HStack {
            Text(verbatim: title ?? "")
        }
    }
}

...
struct BrowserView: View {

    @StateObject var webViewStore = WebViewStore()

    var body: some View {
        VStack {
               BrowserTitleBarView(title: webViewStore.binding(for: \.title))
               ...
               }
       }

I am not an expert on SwiftUI. Is there a better way without creating the extension?

Thanks.

[kylehickinson]

Hey @piterwilson, what you're describing actually exists already in SwiftUI. The API is called Binding.constant(_:) which lets you create a Binding out of something that isn't mutable. This would let you do something like:

BrowserTitleBarView(title: .constant(webViewStore.title))

However you don't need to make variables in your View a Binding just to pass info in, you can just do var title: String? for instance and just pass in the title directly. Bindings are usually only used when you want the View to be able to mutate something a parent passes in.

Let me know if that helps!