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

Question

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"

// Singleton
static 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!

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