A simple rule applies to both OS X and iOS apps: if localized resources aren’t present for a user’s locale, the native development region will be used.
This can be set in your app’s Info.plist:
You may have noticed that iOS and Mac OS allow regional dialect subsets of certain languages. For example, you app may be localized in Spanish and Argentinian Spanish. Your set up would look something like this:
The first resource folder is what you define as Spanish. Let’s say European Spanish. The second folder (es_AR) is where you keep your Argentinian Spanish localization.
If you are in Spain and open the app, you get the es.lproj Spanish. If you are in Argentina, you get the Argentinian Spanish. What if you are in Chile?
We haven’t defined a es_CL.lproj folder, so the app will launch in the dialect’s parent language, in this case, es.lproj.
If you don’t have an es.lproj folder however, but only an es_ES.lproj and an es_AR.lproj folder, then Chilean users will get the app’s native development language, usually English (see above).
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