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

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.