Force a localization of Paywall to a specific Language in ObjectiveC project

Hi.. I’ve got an old ObjC project that uses RevCat.  I don’t rely on the system localization but allow the user to choose the language to override it.. so I want to also override the paywall localization. 

I found another post that says this is possible in ios:

Purchases.shared.overridePreferredUILocale("es")

My app is ObjC and generally I can call any func with objC but this one doesn't seem to be found.. trying:

[[RCPurchases sharedPurchases] overridePreferredUILocale:@”es”];

But that’s not found.. is there a way? Or would I need to switch over and have some swift in my project (I haven’t really done that, I know it’s possible.. just trying to find the easiest solution at the moment)

Thanks!

D