iPhone: Change Keyboard language programmatically

I know it is old question, but here it is my way to change keyboard language.

Thank to @the4kman for the mark: this way can change current keyboard only to those which were added in Settings.

Swift 3:

class CustomTextField: UITextField {

    private func getKeyboardLanguage() -> String? {
        return "en" // here you can choose keyboard any way you need
    }

    override var textInputMode: UITextInputMode? {
        if let language = getKeyboardLanguage() {
            for tim in UITextInputMode.activeInputModes {
                if tim.primaryLanguage!.contains(language) {
                    return tim
                }
            }
        }
        return super.textInputMode
    }

}

You can do it starting from iOS 7 on a per UIResponder basis. There is textInputMode property in UIResponder class. It is readonly, but the documentation says:

The text input mode identifies the language and keyboard displayed when this responder is active.

For responders, the system normally displays a keyboard that is based on the user’s language preferences. You can redefine this property and use it to return a different text input mode in cases where you want a responder to use a specific keyboard. The user can still change the keyboard while the responder is active, but switching away to another responder and then back restores the keyboard you specified.

In my project I created a subclass of UITextField and defined a new property called userDefinedKeyboardLanguage. I also overrode above mentioned textInputMode method. It looks similar to the following:

- (UITextInputMode *) textInputMode {
    for (UITextInputMode *tim in [UITextInputMode activeInputModes]) {
        if ([[Utilities langFromLocale:userDefinedKeyboardLanguage] isEqualToString:[Utilities langFromLocale:tim.primaryLanguage]]) return tim;
    }
    return [super textInputMode];
}

I have also a custom method +(NSString *)langFromLocale:(NSString *)locale in my Utilities class which looks like this:

+ (NSString *)langFromLocale:(NSString *)locale {
    NSRange r = [locale rangeOfString:@"_"];
    if (r.length == 0) r.location = locale.length;
    NSRange r2 = [locale rangeOfString:@"-"];
    if (r2.length == 0) r2.location = locale.length;
    return [[locale substringToIndex:MIN(r.location, r2.location)] lowercaseString];
}

Now my custom textfield class can change the keyboard input language simply by setting userDefinedKeyboardLanguage property to the desired language.