If the screen which you want to A/B test is not the first screen, you can make background calls to your server and based on result decide which screen to show.

If the screen which you want to A/B test is not the first screen, you can make background calls to your server and based on result decide which screen to show. Write to user settings when you want to permanently disable it. Note: i) Reasoning behind not having it as first screen as it really slows the application launch. ii) You should make sure that if webservice call takes too long, just pick one default which is shown to user instead of waiting for result iii) if you really want to do it for first screen, load and save the result in user settings for next launch while the application is running