Changing language on the fly, in running iOS, programmatically

Question

I\'ve been stackling and googling for hours. And I\'m kind of desperate now. I would like to change the language of my application inside the app not only with the default l

Answer 1

This is an old question, but i was developing an helper that notifies me when the language change on the fly.

Take a look at the code of helper:

import Foundation

class LocalizableLanguage {

    // MARK: Constants

    fileprivate static let APPLE_LANGUAGE_KEY = "AppleLanguages"

    /// Notification Name to observe when language change
    static let ApplicationDidChangeLanguage = Notification.Name("ApplicationDidChangeLanguage")

    // MARK: Properties

    /// An array with all available languages as String
    static var availableLanguages: [String]? = {
        return UserDefaults.standard.object(forKey: APPLE_LANGUAGE_KEY) as? [String]
    }()

    /// The first element of available languages that is the current language
    static var currentLanguageCode: String? = {
        return availableLanguages?.first
    }()

    /// The current language code with just 2 characters
    static var currentShortLanguageCode: String? = {
        guard let currentLanguageCode = currentLanguageCode else {
            return nil
        }

        let strIndex = currentLanguageCode.index(currentLanguageCode.startIndex, offsetBy: 2)
        return currentLanguageCode.substring(to: strIndex)
    }()

    // MARK: Handle functions

    /// This accepts the short language code or full language code
    /// Setting this will send a notification with name "ApplicationDidChangeLanguage", that can be observed in order to refresh your localizable strings
    class func setLanguage(withCode langCode: String) {

        let matchedLangCode = availableLanguages?.filter {
            $0.contains(langCode)
        }.first

        guard let fullLangCode = matchedLangCode else {
            return
        }

        var reOrderedArray = availableLanguages?.filter {
            $0.contains(langCode) == false
        }

        reOrderedArray?.insert(fullLangCode, at: 0)

        guard let langArray = reOrderedArray else {
            return
        }

        UserDefaults.standard.set(langArray, forKey: APPLE_LANGUAGE_KEY)
        UserDefaults.standard.synchronize()

        LocalizableLanguage.refreshAppBundle()

        NotificationCenter.default.post(name: ApplicationDidChangeLanguage, object: fullLangCode)
    }
}

// MARK: Refresh Bundle Helper

private extension LocalizableLanguage {

    class func refreshAppBundle() {
        MethodSwizzleGivenClassName(cls: Bundle.self, originalSelector: #selector(Bundle.localizedString(forKey:value:table:)), overrideSelector: #selector(Bundle.specialLocalizedStringForKey(_:value:table:)))
    }

    class func MethodSwizzleGivenClassName(cls: AnyClass, originalSelector: Selector, overrideSelector: Selector) {
        let origMethod: Method = class_getInstanceMethod(cls, originalSelector);
        let overrideMethod: Method = class_getInstanceMethod(cls, overrideSelector);
        if (class_addMethod(cls, originalSelector, method_getImplementation(overrideMethod), method_getTypeEncoding(overrideMethod))) {
            class_replaceMethod(cls, overrideSelector, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
        } else {
            method_exchangeImplementations(origMethod, overrideMethod);
        }
    }
}

extension Bundle {

    func specialLocalizedStringForKey(_ key: String, value: String?, table tableName: String?) -> String {

        let availableLanguages = UserDefaults.standard.object(forKey: LocalizableLanguage.APPLE_LANGUAGE_KEY) as? [String]
        let currentLanguageCode = availableLanguages?.first ?? "en-US"
        let currentShortLanguageCode = currentLanguageCode.substring(to: currentLanguageCode.index(currentLanguageCode.startIndex, offsetBy: 2))

        let path =
                Bundle.main.path(forResource: currentLanguageCode, ofType: "lproj") ??
                Bundle.main.path(forResource: currentShortLanguageCode, ofType: "lproj") ??
                Bundle.main.path(forResource: "Base", ofType: "lproj")

        guard
            self == Bundle.main,
            let bundlePath = path,
            let bundle = Bundle(path: bundlePath)
        else {
            return self.specialLocalizedStringForKey(key, value: value, table: tableName)
        }

        return bundle.specialLocalizedStringForKey(key, value: value, table: tableName)
    }
}

You just need to copy that code and put in your project.

Then, you simple implement the listener like this:

NotificationCenter.default.addObserver(forName: LocalizableLanguage.ApplicationDidChangeLanguage, object: nil, queue: nil) { notification in
            guard let langCode = notification.object as? String else {
                return
            }
            self.accountStore.languageCode.value = langCode
        } 

Note that this line self.accountStore.languageCode.value = langCode is what i need to refresh when the app language as changed, then i can easily change all strings of my ViewModels in order to change the language to the user immediately.

In order to change the language, you can just call:

LocalizableLanguage.setLanguage(withCode: "en")

Other helper that could be nice to you is:

import Foundation

extension String {

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

}

So if you have in your localizable files something like that:

main.view.title = "Title test";

You can simple call:

"main.view.title".localized

And you have your string translated.