manual language selection in an iOS-App (iPhone and iPad)

In the meantime I did find a solution for my problem on myself:

I created a new class "LocalizeHelper":

Header LocalizeHelper.h

//LocalizeHelper.h#import <Foundation/Foundation.h>// some macros (optional, but makes life easy)// Use "LocalizedString(key)" the same way you would use "NSLocalizedString(key,comment)"#define LocalizedString(key) [[LocalizeHelper sharedLocalSystem] localizedStringForKey:(key)]// "language" can be (for american english): "en", "en-US", "english". Analogous for other languages.#define LocalizationSetLanguage(language) [[LocalizeHelper sharedLocalSystem] setLanguage:(language)]@interface LocalizeHelper : NSObject// a singleton:+ (LocalizeHelper*) sharedLocalSystem;// this gets the string localized:- (NSString*) localizedStringForKey:(NSString*) key;//set a new language:- (void) setLanguage:(NSString*) lang;              @end

iMplementation LocalizeHelper.m

// LocalizeHelper.m#import "LocalizeHelper.h"// Singletonstatic LocalizeHelper* SingleLocalSystem = nil;// my Bundle (not the main bundle!)static NSBundle* myBundle = nil;@implementation LocalizeHelper//-------------------------------------------------------------// allways return the same singleton//-------------------------------------------------------------+ (LocalizeHelper*) sharedLocalSystem {    // lazy instantiation    if (SingleLocalSystem == nil) {        SingleLocalSystem = [[LocalizeHelper alloc] init];    }    return SingleLocalSystem;}//-------------------------------------------------------------// initiating//-------------------------------------------------------------- (id) init {    self = [super init];    if (self) {        // use systems main bundle as default bundle        myBundle = [NSBundle mainBundle];    }    return self;}//-------------------------------------------------------------// translate a string//-------------------------------------------------------------// you can use this macro:// LocalizedString(@"Text");- (NSString*) localizedStringForKey:(NSString*) key {    // this is almost exactly what is done when calling the macro NSLocalizedString(@"Text",@"comment")    // the difference is: here we do not use the systems main bundle, but a bundle    // we selected manually before (see "setLanguage")    return [myBundle localizedStringForKey:key value:@"" table:nil];}//-------------------------------------------------------------// set a new language//-------------------------------------------------------------// you can use this macro:// LocalizationSetLanguage(@"German") or LocalizationSetLanguage(@"de");- (void) setLanguage:(NSString*) lang {    // path to this languages bundle    NSString *path = [[NSBundle mainBundle] pathForResource:lang ofType:@"lproj" ];    if (path == nil) {        // there is no bundle for that language        // use main bundle instead        myBundle = [NSBundle mainBundle];    } else {        // use this bundle as my bundle from now on:        myBundle = [NSBundle bundleWithPath:path];        // to be absolutely shure (this is probably unnecessary):        if (myBundle == nil) {            myBundle = [NSBundle mainBundle];        }    }}@end

For each language you want to support you need a file named Localizable.strings. This works exactly as described in Apples documentation for localization. The only difference: Now you even can use languages like hindi or esperanto, that are not supported by Apple.

To give you an example, here are the first lines of my english and german versions of Localizable.strings:

English

/* English - English *//* for debugging */"languageOfBundle" = "English - English";/* Header-Title of the Table displaying all lists and projects */"summary" = "Summary";/* Section-Titles in table "summary" */"help" = "Help";"lists" = "Lists";"projects" = "Projects";"listTemplates" = "List Templates";"projectTemplates" = "Project Templates";

German

/* German - Deutsch *//* for debugging */"languageOfBundle" = "German - Deutsch";/* Header-Title of the Table displaying all lists and projects */"summary" = "Überblick";/* Section-Titles in table "summary" */"help" = "Hilfe";"lists" = "Listen";"projects" = "Projekte";"listTemplates" = "Vorlagen für Listen";"projectTemplates" = "Vorlagen für Projekte";

To use localizing, you must have some settings-routines in your app, and in the language-selection you call the macro:

LocalizationSetLanguage(selectedLanguage);

After that you must enshure, that everything that was displayed in the old language, gets redrawn in the new language right now (hidden texts must be redrawn as soon as they get visible again).

To have localized texts available for every situation, you NEVER must write fix texts to the objects titles. ALWAYS use the macro LocalizedString(keyword).

don't:

cell.textLabel.text = @"nice title";

do:

cell.textLabel.text = LocalizedString(@"nice title");

and have a "nice title" entry in every version of Localizable.strings!

Simply add the following to the screen with language choice:

    NSString *tempValue = //user chosen language. Can be picker view/button/segmented control/whatever. Just get the text out of it    NSString *currentLanguage = @"";    if ([tempValue rangeOfString:NSLocalizedString(@"English", nil)].location != NSNotFound) {        currentLanguage = @"en";    } else if ([tempValue rangeOfString:NSLocalizedString(@"German", nil)].location != NSNotFound) {        currentLanguage = @"de";    } else if ([tempValue rangeOfString:NSLocalizedString(@"Russian", nil)].location != NSNotFound) {        currentLanguage = @"ru";    }    [[NSUserDefaults standardUserDefaults] setObject:[NSArray arrayWithObjects:currentLanguage, nil] forKey:@"AppleLanguages"];    [[NSUserDefaults standardUserDefaults]synchronize];

Then ask them to restart the app and the app will be in other language.

Hope it helps

Here's a ready-to-use and step-by-step guide on how to use Novarg's approach in Swift 3:

Step #1: Implement a language chooser

How to best do this is up to you and depends on the project. But use

Bundle.main.localizations.filter({ $0 != "Base" }) // => ["en", "de", "tr"]

to get a list of all your supported locales language codes programmatically. Also you can use

Locale.current.localizedString(forLanguageCode: "en") // replace "en" with your variable

to present the language name in the apps current language.

As a complete example you could present a popover action sheet after clicking a button like this:

@IBOutlet var changeLanguageButton: UIButton!@IBAction func didPressChangeLanguageButton() {    let message = "Change language of this app including its content."    let sheetCtrl = UIAlertController(title: "Choose language", message: message, preferredStyle: .actionSheet)    for languageCode in Bundle.main.localizations.filter({ $0 != "Base" }) {        let langName = Locale.current.localizedString(forLanguageCode: languageCode)        let action = UIAlertAction(title: langName, style: .default) { _ in            self.changeToLanguage(languageCode) // see step #2        }        sheetCtrl.addAction(action)    }    let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)    sheetCtrl.addAction(cancelAction)    sheetCtrl.popoverPresentationController?.sourceView = self.view    sheetCtrl.popoverPresentationController?.sourceRect = self.changeLanguageButton.frame    present(sheetCtrl, animated: true, completion: nil)}

Step #2: Explain user what to do + Change language with restart

You might have noticed that the code in step #1 calls a method named changeToLanguage(langCode:). That's what you should do, too when the user chooses a new language to change to, no matter how you designed your chooser. Here's its implementation, just copy it to your project:

private func changeToLanguage(_ langCode: String) {    if Bundle.main.preferredLocalizations.first != langCode {        let message = "In order to change the language, the App must be closed and reopened by you."        let confirmAlertCtrl = UIAlertController(title: "App restart required", message: message, preferredStyle: .alert)        let confirmAction = UIAlertAction(title: "Close now", style: .destructive) { _ in            UserDefaults.standard.set([langCode], forKey: "AppleLanguages")            UserDefaults.standard.synchronize()            exit(EXIT_SUCCESS)        }        confirmAlertCtrl.addAction(confirmAction)        let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)        confirmAlertCtrl.addAction(cancelAction)        present(confirmAlertCtrl, animated: true, completion: nil)    }}

This will both ask and inform the user about if he wants to do the change and how to do it. Also it sets the apps language on the next start using:

UserDefaults.standard.set([langCode], forKey: "AppleLanguages")UserDefaults.standard.synchronize() // required on real device

Step #3 (optional): Localize the Strings

You might want to localize the strings like "Close now" by using the NSLocalizedString macro (or any other enhanced method).

Real World Example

I'm using this exact implementation in an app targeted for iOS 10, I can confirm it works for me both on simulator and device. The app is actually open source, so you can find the above code distributed into different classes here.