How to get string value from LocalizedStringKey?

I'm localizing my SwiftUI app with using LocalisedStringKey and the help of the following code:

Text(l10n.helloWorld)

Where l10n is:

enum l10n {
   internal static let helloWorld = LocalizedStringKey("hello.world")
}

Where "hello.world" is defined in the file Localizable.strings:

"hello.world" = "Hello world !";

While this code works in SwiftUI's View like this:

...
Text(i18n.helloWorld)
...

I can't find a way to get l10n value from LocalizedStringKey in code behind like this:

l10n.helloWorld.toString()

I think it's because SwiftUI is not mean't to do localization from code behind, all localization must happen in view declaration.

However there's a way to achieve that via extensions methods :

extension LocalizedStringKey {

    /**
     Return localized value of thisLocalizedStringKey
     */
    public func toString(arguments: CVarArg...) -> String {
        //use reflection
        let mirror = Mirror(reflecting: self)
        
        //try to find 'key' attribute value
        let attributeLabelAndValue = mirror.children.first { (arg0) -> Bool in
            let (label, _) = arg0
            if(label == "key"){
                return true;
            }
            return false;
        }
        
        if(attributeLabelAndValue != nil) {
            //ask for localization of found key via NSLocalizedString
            return String.localizedStringWithFormat(NSLocalizedString(attributeLabelAndValue!.value as! String, comment: ""), arguments);
        }
        else {
            return "Swift LocalizedStringKey signature must have changed. @see Apple documentation."
        }
    }
}

Sadly you must use Reflection to achieve that as key has an internal level of protection in LocalizedStringKey, use at your own risks.

Use asis :

let s = l10n.helloWorld.toString();