IBInspectable Localization in Storyboards.

Localization+IBInspectable.m

// MARK : Localization+IBInspectable.h

@interface UILabel(Localization)
    @property (nonatomic, weak) IBInspectable NSString *localizationId;
@end

@interface UIButton(Localization)
    @property (nonatomic, weak) IBInspectable NSString *localizationId;
@end

@interface UITextField(Localization)
    @property (nonatomic, weak) IBInspectable NSString *placeholderLocalizationId;
@end

@interface UITextView(Localization)
    @property (nonatomic, weak) IBInspectable NSString *localizationId;
@end


// MARK : Localization+IBInspectable.m

NS_INLINE BOOL isEngLang() {
    NSString* language = [[NSLocale preferredLanguages] objectAtIndex:0];
    return [[language lowercaseString] hasPrefix:@"en"];
}

NS_INLINE NSAttributedString* formatCharXMLTagsUsingAttributes(NSString *string,
                                                               UIFont *font, UIColor *textColor){
    NSDictionary *options = @{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
                              NSCharacterEncodingDocumentAttribute: @(NSUTF8StringEncoding)};
    NSMutableAttributedString *mutAttrString = [[NSMutableAttributedString alloc] initWithData:[string dataUsingEncoding:NSUTF8StringEncoding]
                                            options: options
                                 documentAttributes: nil error:nil];
    [mutAttrString addAttribute:NSFontAttributeName value:font range: NSMakeRange(0, mutAttrString.string.length)];
    [mutAttrString addAttribute:NSForegroundColorAttributeName value:textColor range: NSMakeRange(0, mutAttrString.string.length)];
    return mutAttrString;
}

@implementation UILabel(Localization)
- (void)setLocalizationId:(NSString *)localizationId {
    if (localizationId.length == 0 || isEngLang())
        return;
    NSString *localized = NSLocalizedString(localizationId, nil);
    if (localized.length == 0) {
        return;
    }
    self.text = localized;
}
- (NSString *)localizationId {
    return @"";
}
@end

@implementation UIButton(Localization)

- (void)setLocalizationId:(NSString *)localizationId {
    if (localizationId.length == 0 || isEngLang())
        return;
    NSString *localized = NSLocalizedString(localizationId, nil);
    if (localized.length == 0) {
        return;
    }
    if (self.currentAttributedTitle.string.length > 0) {
        NSAttributedString *attrString = formatCharXMLTagsUsingAttributes(localized,
                                                                          self.titleLabel.font,
                                                                          self.titleLabel.textColor);

        [self setAttributedTitle: attrString forState:UIControlStateNormal];
    } else {
        [self setTitle: localized forState: UIControlStateNormal];
    }
}
- (NSString *)localizationId {
    return @"";
}
@end

@implementation UITextView(Localization)
    
- (void)setLocalizationId:(NSString *)localizationId {
    if (localizationId.length == 0 || isEngLang())
    return;
    NSString *localized = NSLocalizedString(localizationId, nil);
    if (localized.length == 0) {
        return;
    }
    if (self.attributedText.string.length > 0) {
        self.attributedText = formatCharXMLTagsUsingAttributes(localized, self.font, self.textColor);
    } else {
        self.text = localized;
    }
}
- (NSString *)localizationId {
    return @"";
}
@end


@implementation UITextField(Localization)
- (void)setPlaceholderLocalizationId:(NSString *)placeholderLocalizationId {
    if (placeholderLocalizationId == 0 || isEngLang())
        return;
    NSString *localized = NSLocalizedString(placeholderLocalizationId, nil);
    if (localized.length == 0)
        return;
    self.placeholder = localized;
}
- (NSString *)placeholderLocalizationId {
    return @"";
}

@end