How to store object in iOS (Objective-C) and Android (Java) in a React Native App

I'm developing an app in React Native. I have to do something in native side (Objective-C for iOS and Java for Android).

I get after log in an object :

{"success":"true", "action":"logged", "email":"email@gmail.com", "password":"1234567:wZ", "id":"1"}

I want to store that object on native side and use the email to initiate some native module but I don't know how to do it.I can do it easily on React Native tho.

So what I would like to do is :

1. Save the object
2. Get the email of the object
3. Use the email in something like this : [customFieldsDictionary setObject:@"email" forKey:@"f_EMail"];

Anyone can help me please ? This is totally new for me.Thank you very much!