Language change in the app locally

I am developing an app witch support 3 language Telugu,Hindi,English... Now my requirement is if when I click the Telugu button my whole app need to change to Telugu vise versa to remaining language, I have language IDs for each language te=1,hi=2,en=3 Before calling API I need to append the language id to all the APIs in my all classes for respective results according to language ids, I saved the 3 language ids in NSuser default s, failing to append the language IDs to API Parameters

Failing to write if statement for this

Please help me on this, stuck on this since 10 days