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

Ok, although it's an old question with an accepted answer, I will answer it anyway.

For those who wants to check whether the device language is RTL, independent if your application supports or not this language, you should use [NSLocale characterDirectionForLanguage:] like this:

+ (BOOL)isDeviceLanguageRightToLeft {

    NSLocale *currentLocale = [NSLocale currentLocale];
    NSLocaleLanguageDirection direction = [NSLocale characterDirectionForLanguage:[currentLocale objectForKey:NSLocaleLanguageCode]];
    return (direction == NSLocaleLanguageDirectionRightToLeft);
}

The code above will return YES if your app only supports english, but your device is set to Arabic for example.

Apple recommends that you use [UIApplication sharedApplication].userInterfaceLayoutDirection, just because it returns the direction based on the language that your app is using (has support to). Here is the code snippet:

+ (BOOL)isAppLanguageRightToLeft {

    NSLocaleLanguageDirection direction = [UIApplication sharedApplication].userInterfaceLayoutDirection;
    return (direction == UIUserInterfaceLayoutDirectionRightToLeft);
}

The code above will return NO when your app only supports english, but your device is set to Arabic for example.

Answer 2

if ([[UIDevice currentDevice].systemVersion floatValue] >= 9.0) {
    if ([UIView userInterfaceLayoutDirectionForSemanticContentAttribute:self.view.semanticContentAttribute] == UIUserInterfaceLayoutDirectionRightToLeft) {
        NSLog(@"Right to left");
    }
    else{
        NSLog(@"left to Right");
    }
} else {
    /* Use the previous technique */
    //Work for earlier ios 6 to ios 10
    if ([NSLocale characterDirectionForLanguage:[[NSLocale preferredLanguages] objectAtIndex:0]] == NSLocaleLanguageDirectionRightToLeft) {
        NSLog(@"Right to left");
    }
    else{
        NSLog(@"left to Right");
    }
}

must watch Advanced Topics in Internationalization wwdc2014

Answer 3

if you want to check if the device is running in RTL or LTR in swift 3

if(UIApplication.shared.userInterfaceLayoutDirection == UIUserInterfaceLayoutDirection.rightToLeft) {
    //RTL
} else {
   //LTR
}

Answer 4

Rose Perrone is completely correct. However the use of dispatch_once in a getter for a simple boolean value - is really too much overhead. Unnecessary use of dispatch once. Because you will probably want to use that many times inside a layout or drawing function.

So you have two faster options:

+ (BOOL)isRtl
{
    static BOOL isRtl = NO;
    static BOOL isRtlFound = NO;
    if (!isRtlFound)
    { // This is "safe enough". Worst case is this code will be called twice in the app's lifecycle...
        isRtl = [NSLocale characterDirectionForLanguage:[NSBundle mainBundle].preferredLocalizations[0]] == NSLocaleLanguageDirectionRightToLeft;
        isRtlFound = YES;
    }
    return isRtl;
}

Or just cache it in a static variable, using the static constructor:

static BOOL s_isRtl = NO;
+ initialize
{
    s_isRtl = [NSLocale characterDirectionForLanguage:[NSBundle mainBundle].preferredLocalizations[0]] == NSLocaleLanguageDirectionRightToLeft;
}

Note that this will actually share the static variable between any class that uses this code.

Answer 5

Thanks to Kevin Ballard's answer I was able to create the following utility function to do this:

+ (BOOL)isDeviceLanguageRTL {
   return [NSLocale characterDirectionForLanguage:[[NSLocale currentLocale] objectForKey:NSLocaleLanguageCode]]==NSLocaleLanguageDirectionRightToLeft;
}