Class for user actions

Question

I implemented a class for relationships with the user (deletion, name change, check for existence), I created this class to remove extra logic from the activity class. Could you talk about how my code can be improved?

class UserActionManager @Inject constructor(private val repository : BaseAppRepository,
 private val sharedPreferences : JsonSharedPreferences) {
 fun editUserName(user: User,newUserName: String) {
 Completable.fromAction {
 val userObjective:Objective? = sharedPreferences.loadObject(GlobalConstants.OBJECTIVE_SAVE_KEY + user.userName,Objective::class.java)
 val userProfile:Profile? = sharedPreferences.loadObject(GlobalConstants.PROFILE_SAVE_KEY + user.userName,Profile::class.java)
 sharedPreferences.saveObject<Objective>(GlobalConstants.OBJECTIVE_SAVE_KEY + newUserName, userObjective)
 sharedPreferences.saveObject<Profile>(GlobalConstants.PROFILE_SAVE_KEY + newUserName, userProfile)
 repository.updateUserName(user.userName, newUserName)
 user.userName = newUserName
 repository.updateUser(user)
 }.subscribeOn(Schedulers.io()).subscribe()
 }
 fun deleteUser(user: User) {
 Completable.fromAction { repository.deleteUser(user) }.subscribeOn(Schedulers.io()).subscribe()
 sharedPreferences.saveObject<Objective>(GlobalConstants.OBJECTIVE_SAVE_KEY + user.userName, null)
 sharedPreferences.saveObject<Profile>(GlobalConstants.PROFILE_SAVE_KEY + user.userName, null)
 }
 fun isEmptyUser(userName: String): Single<Boolean> {
 return repository.getUserByUserName(userName)
 .subscribeOn(Schedulers.io())
 .isEmpty
 }
}

• tieskedh: Search for kotlin - coroutines. This is the Kotlin-version for RX with a lot of syntactic sugar maybe medium.com/@daptronic/… can help

Answer 1

• Extract your preferences code into extra class or create extension functions to get those objects. Ex. sharedPreferences.loadObject(GlobalConstants.OBJECTIVE_SAVE_KEY + user.userName,Objective::class.java) should have it's own method. Ex. loadUserByName.
• You are using kotlin, use it's strengths like non-nullables by default. Does repository.updateUserName() really accept nullables? That seems wrong. I'd use it for example with elvis operator loadUserByName(user.username) ?: error("username not found")