ios – LocalizedStringKey interpolated with the worth of one other LocalizedStringKey

For the reason that localised string has format specifiers, you also needs to add the format specifiers to the important thing.

// .strings:

"turn_off_feature_format %@" = "Flip off %@";
"feature_1_title" = "Characteristic 1";
"feature_2_title" = "Characteristic 2";

Because of the customized string interpolation offered by LocalizedStringKey.StringInterpolation, this lets you immediately format the string when making a LocalizedStringKey.

// this creates a LocalizedStringKey similar to 
// the "turn_off_feature_format %@" key within the .strings file,
// with the placeholder changed with no matter "characteristic" is
let key: LocalizedStringKey = "turn_off_feature_format (characteristic)"

If characteristic is a LocalizedStringResource, it will get localised too.

Figuring out that, we will write one thing like this:

extension LocalizedStringKey {
    static func turnOff(characteristic: LocalizedStringResource) -> LocalizedStringKey {
        "turn_off_feature_format (characteristic)"
    }
}

extension LocalizedStringResource {
    static let feature1 = Self("feature_1_title")
    static let feature2 = Self("feature_2_title")
}

(Additionally take into account making an enum to symbolize the options)

Then you’ll be able to create Textual contents like this:

Textual content(.turnOff(characteristic: .feature1))
Textual content(.turnOff(characteristic: .feature2))

// this additionally works:
Textual content(.feature1)

If you cannot change the localisation keys, I feel you might be caught with utilizing String(format:_:) to do the formatting. I am unsure why you might be struggling to eliminate the duplicate string literal although. It will possibly simply be extracted to a different computed property:

var format: String {
    String(localized: "turn_off_feature_format")
}

extension LocalizedStringKey {
  static var turnOffFeature1: Self {
    LocalizedStringKey(stringLiteral: String(
      format: format, 
      String(localized: "feature_1_title")
    ))
  }
  static var turnOffFeature2: Self {
    LocalizedStringKey(stringLiteral: String(
      format: format, 
      String(localized: "feature_2_title")
    ))
  }
}

That mentioned, it would not make sense for these to be LocalizedStringKeys anymore, since you do not even have a keys known as Flip off Characteristic 1 and so forth. These ought to simply be Strings. I might put them in an enum:

enum Options: String {
    case feature1 = "feature_1_title"
    case feature2 = "feature_2_title"
    
    non-public static var format: String {
        String(localized: "turn_off_feature_format")
    }
    
    var turnOffLocalized: String {
        String(
            format: Self.format,
            String(localized: .init(rawValue))
        )
    }
    
    // for getting solely the names of the options
    var key: LocalizedStringKey {
        .init(rawValue)
    }
}

e.g.

Textual content(Options.feature1.key)
Textual content(Options.feature1.turnOffLocalized)