iOS: Determine if device language is Right to Left (RTL)

Question

Is there a way to easily determine if the language the device is set to is right to left (RTL)?

Answer 1

NSLocale has two methods +characterDirectionForLanguage: and +lineDirectionForLanguage:. The first is presumably Left-to-Right vs Right-to-Left and the second is Top-to-Bottom vs Bottom-to-Top. You can pass it the result of [[NSLocale currentLocale] objectForKey:NSLocaleLanguageCode].

Update:

The original question asked was how to determine whether the device language is RTL. Using +[NSLocale characterDirectionForLanguage:] and +[NSLocale lineDirectionForLanguage:] is unambiguously correct for that; you can pass either [[NSLocale currentLocale] objectForKey:NSLocaleLanguageCode] or [NSLocale preferredLanguages][0] to that to get the relevant info (I'm not sure offhand whether the NSLocaleLanguageCode uses the preferred language, or the set region).

However, it's very likely that what the original poster actually wanted to know is whether the application's interface should be laid out in RTL or LTR. This is very similar to asking what the direction of the language is, except it takes the application's available localizations into account. If the application is not localized into the user's preferred language, it will use a non-preferred language instead. And the answer to this question is to use [UIApplication sharedApplication].userInterfaceLayoutDirection.