How to assign an optional Binding parameter in SwiftUI?

Question

I\'m trying to build a custom NavBar with some optional Views, like a searchbar (but only if the view needs to display it).

I need to pass

Answer 1

What you want is an Optional Binding of a String, not a Binding of an Optional String. I don't think you can achieve that by using the @Binding annotation.

However, you don't need to used the annotation. You can just declare the variable as a Binding:

Your

@Binding var searchTxt: String?;

then turns to this

var searchTxt: Binding<String?>

But this way the syntax lets you place the ? wherever you want. So if you move it to the end, after the Binding's closing tag, you have what you want.

var searchTxt: Binding<String>?

If you want to access the String inside your Binding, you have to use the wrappedValue property.

Text(searchTxt!.wrappedValue)

Answer 2

@Binding var searchTxt: String?

init(searchTxt: Binding<String?>?) {
    self._searchTxt = searchTxt ?? Binding.constant(nil)
}

Answer 3

So below is example to use optional Binding and how to access the binding and toggle to show some view:

struct NavBar: View {
    @Binding var showUser: Bool
    var showOptional: Binding<Bool>?
    
    var body: some View {
    
    VStack {
     Button(action: { showUser.toggle() },
            label: { Text("NOT OPTIONAL") })
    
     Button(action: { showSelectBuddy?.wrappedValue.toggle()) },
            label: { Text("NOT OPTIONAL") })
    
    }
    }
    }

    struct UseNavbar: View {
    
    @State var showoptional = false
    @State var show = false 
    
    var body: some View {
    Text("Optional")
    .navigationBarItems(leading:
    NavBar(showUser: show), trailing: NavBar(showUser: show, showOptional: showoptional))
    }
    }

Answer 4

I have a UIViewControllerRepresentable in order to use UIImagePickerController. If you've ever used this image picker, you know that you need to image returned to be an optional. So in my ContentView I declared:

@State var uiImage: UIImage?

...

if uiImage != nil {
    Image(uiImage: $uiImage
} else {
    Rectangle()
}

And in my ImagePicker (that's my SwiftUI view) I have:

@Binding var uiImage: UIImage?

Works like a charm.

(The if statement is pretty much psuedo-code, as I'm actually using an MTKView and a CIImage, but your get the drift - you use the optional just as you would anywhere else.)