How to use NSLocalizedString function with variables in Swift?

I'm trying to localize my app using NSLocalizedString. When I import the XLIFF file, most works like a charm but something do not and some string is not localized. I have noticed that the problem is from NSLocalizedString containing something variable inside like:

NSLocalizedString(" - \(count) Notifica", comment: "sottotitolo prescrizione per le notifiche al singolare")

or

NSLocalizedString("Notifica per \(medicina!) della prescrizione \(prescription!)\nMemo: \(memoTextView.text)", comment: "Messaggio della Local Notification")

Maybe this is not the correct syntax for this kind of stuff. Someone can explain me how to do that in Swift?

You can use the sprintf format parameters within NSLocalizedString, so your example can look like this:

let myString = String(format: NSLocalizedString(" - %d Notifica", comment: "sottotitolo prescrizione per le notifiche al singolare"), count)

In Session #412 of the WWDC2014 "Localizing with Xcode 6" the proper way to this in Swift is the following:

String.localizedStringWithFormat(
    NSLocalizedString(" - %d Notifica",
    comment: "sottotitolo prescrizione per le notifiche al singolare"),
    count)

I have followed the approach of creating extension to String as i have many strings to localize.

extension String {
    var localized: String {
        return NSLocalizedString(self, comment:"")
    }
}

To use it for localization in code do:

self.descriptionView.text = "Description".localized

For strings with dynamic variables follow :

self.entryTimeLabel.text = "\("Doors-open-at".localized) \(event.eventStartTime)"

Declare the strings in String files for different languages (example : Arabic and English)

Hope will be helping!

I tried the above solutions however the code below worked for me

SWIFT 4

extension String {

    /// Fetches a localized String
    ///
    /// - Returns: return value(String) for key
    public func localized() -> String {
        let path = Bundle.main.path(forResource: "en", ofType: "lproj")
        let bundle = Bundle(path: path!)
        return (bundle?.localizedString(forKey: self, value: nil, table: nil))!
    }


    /// Fetches a localised String Arguments
    ///
    /// - Parameter arguments: parameters to be added in a string
    /// - Returns: localized string
    public func localized(with arguments: [CVarArg]) -> String {
        return String(format: self.localized(), locale: nil, arguments: arguments)
    }

}

// variable in a class
 let tcAndPPMessage = "By_signing_up_or_logging_in,_you_agree_to_our"
                                     .localized(with: [tAndc, pp, signin])

// Localization File String
"By_signing_up_or_logging_in,_you_agree_to_our" = "By signing up or logging in, you agree to our \"%@\" and \"%@\" \nAlready have an Account? \"%@\"";

Here is an extension I use in String, it adds a localizeWithFormat function with variable arguments,

extension String {

     func localizeWithFormat(arguments: CVarArg...) -> String{
        return String(format: self.localized, arguments: arguments)        
     }
            
     var localized: String{
         return Bundle.main.localizedString(forKey: self, value: nil, table: "StandardLocalizations")
     }
}

Usage:

let siriCalendarText = "AnyCalendar"
let localizedText = "LTo use Siri with my app, please set %@ as the default list on your device reminders settings".localizeWithFormat(arguments: siriCalendarTitle)

Just be careful not to use the same function and property names that String has. I normally use a 3 letter prefix for all my framework functions.

I wrote the same functions for UILabel

extension UILabel {
    
    func setLocalizedText(key: String) {
        self.text = key.localized
    }
    
    func setLocalizedText(key: String, arguments: [CVarArg]) {
        self.text = String(format: key.localized, arguments: arguments)
    }
}

If you want you can move this localized property to UILabel as well

extension String {
        
    var localized: String{
        return Bundle.main.localizedString(forKey: self, value: nil, table: nil)
    }
}

My localizable

"hi_n" = "Hi, %@!";

Used them like this:

self.greetingLabel.setLocalizedText(key: "hi_n", arguments: [self.viewModel.account!.firstName])
// Shows this on the screen -> Hi, StackOverflow!

I created an extension to String since I had many strings to be localized.

extension String {
    var localized: String {
        return NSLocalizedString(self, tableName: nil, bundle: Bundle.main, value: "", comment: "")
    }
}

For example:

let myValue = 10
let anotherValue = "another value"

let localizedStr = "This string is localized: \(myValue) \(anotherValue)".localized
print(localizedStr)