typical user view model

userViewModel.kt

private val userId = MutableLiveData<String>()

    val userDetails = userId.switchMap {
        userRepo.getUser(it)
    }

    val userFullName = userDetails.map {
        getFullName(it.firstName, it.lastName)
    }

    fun setUserId(userId: String) {
        this.userId.value = userId
    }

    fun getFullName(firstName: String, lastName: String) = "$firstName $lastName"