Setting iOS localization on the fly

NSBundle+RunTimeLanguage.h

#import <Foundation/Foundation.h>

#define RUNTIME_LANGUAGE_STORAGE @"runtimeLanguageStorage"
#define RunTimeLanguageEnglish @"en"
#define RunTimeLanguageSpanish @"es-MX"

#undef NSLocalizedString
#define NSLocalizedString(key, comment) [[NSBundle mainBundle] runTimeLocalizedStringForKey:(key) value:@"" table:nil]

#define setLanguage(x) [[NSUserDefaults standardUserDefaults] setObject:x forKey:RUNTIME_LANGUAGE_STORAGE];  [[NSUserDefaults standardUserDefaults] synchronize];

@interface NSBundle (RunTimeLanguage)

- (NSString *)runTimeLocalizedStringForKey:(NSString *)key value:(NSString *)value table:(NSString *)tableName;

@end

NSBundle+RunTimeLanguage.m

#import "NSBundle+RunTimeLanguage.h"

@implementation NSBundle (RunTimeLanguage)

- (NSString *)runTimeLocalizedStringForKey:(NSString *)key value:(NSString *)value table:(NSString *)tableName {
    NSString *languageCode = [[NSUserDefaults standardUserDefaults] objectForKey:RUNTIME_LANGUAGE_STORAGE];
    
    if ( languageCode == nil ) {
        languageCode = @"en";
    }
    
    NSString *path= [[NSBundle mainBundle] pathForResource:languageCode ofType:@"lproj"];
    NSBundle *languageBundle = [NSBundle bundleWithPath:path];
    NSString *localizedString=[languageBundle localizedStringForKey:key value:key table:nil];
    return localizedString;
}

@end

SomeClass.m

- (IBAction)englishPressed:(id)sender {
    setLanguage(RunTimeLanguageEnglish);
    [self reloadViewUIForTranslationMethod];
}