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Realm DB Implementation Guide

Overview

This document explains the Realm DB implementation in the Reader App for persisting:

  • User feedback with sentiment ratings
  • Favorite books
  • User profile information (username and email)

What Has Been Implemented

1. Realm Database Setup

Dependencies Added

  • Realm Kotlin: io.realm.kotlin:library-base:1.16.0
  • Added to build.gradle.kts with the Realm plugin

Database Models (RealmModels.kt)

Three Realm object models have been created:

  1. FeedbackRealm

    • Stores user feedback submissions
    • Fields: feedback text, sentiment index (0-3), timestamp

  2. FavoriteBookRealm

    • Stores favorite books persistently
    • Fields: book ID, title, author, subtitle, rating, cover image URL, user rating, description

  3. UserProfileRealm

    • Stores user profile information
    • Fields: username, email, last updated timestamp

Database Configuration (RealmDatabase.kt)

  • Singleton pattern for database access
  • Configured with schema version 1
  • Database file: reader_app.realm

2. Repository Layer (RealmRepository.kt)

The repository provides methods for:

Feedback Operations:

  • saveFeedback() - Save new feedback
  • getAllFeedback() - Retrieve all feedback (Flow)
  • deleteFeedback() - Delete specific feedback

Favorite Books Operations:

  • saveFavoriteBook() - Add book to favorites
  • removeFavoriteBook() - Remove book from favorites
  • updateBookRating() - Update user's rating for a book
  • getAllFavoriteBooks() - Get all favorites as Flow<List>
  • isFavorite() - Check if a book is favorited

User Profile Operations:

  • saveUserProfile() - Save/update username and email
  • getUserProfile() - Get profile as Flow
  • getUserProfileOnce() - Get profile once (suspend function)

3. ViewModels Updated

FavoritesViewModel

  • Updated to use Realm DB for persistent storage
  • Constructor now takes RealmRepository
  • Favorites are loaded from Realm on initialization
  • All favorite operations (add/remove/update rating) are persisted to Realm
  • Uses Flow to automatically update UI when database changes

FeedbackViewModel (New)

  • Manages feedback submissions
  • Loads all saved feedback
  • Provides delete functionality

UserProfileViewModel

  • Updated to include Realm DB storage
  • Constructor now takes both UserPreferences and RealmRepository
  • Username is saved to multiple locations for redundancy:
    1. Realm DB (local persistent storage)
    2. UserPreferences (encrypted SharedPreferences)
    3. Firebase Firestore (cloud backup)
  • Fallback hierarchy ensures username is always available

4. UI Screens

YourFeedbackScreen (Updated)

  • Now saves feedback to Realm DB when submitted
  • Uses FeedbackViewModel to persist data
  • Shows confirmation message after saving

ViewFeedbackScreen (New)

  • Displays history of all submitted feedback
  • Shows sentiment icon, rating, text, and timestamp
  • Allows deletion of individual feedback items
  • Empty state when no feedback exists

SavedScreen (Existing - Enhanced)

  • Already displays favorite books
  • Now powered by Realm DB for persistence
  • Favorites survive app restarts

5. Dependency Injection

AppModule

  • Added RealmRepository as singleton

ViewModelModule

  • Updated FavoritesViewModel to receive RealmRepository
  • Added FeedbackViewModel with RealmRepository
  • Updated UserProfileViewModel to receive both UserPreferences and RealmRepository

6. Application Initialization

MyApplication.kt

  • Realm database initialized in onCreate()
  • Happens before Koin initialization

Navigation

New screen added to navigation:

  • ViewFeedbackScreen - Route: ReaderScreens.ViewFeedbackScreen

How to Use

Saving Feedback

// In any composable with FeedbackViewModel injected
feedbackViewModel.saveFeedback("Great app!", sentimentIndex = 3)

Managing Favorites

// In any composable with FavoritesViewModel injected
favoritesViewModel.addFavorite(book)
favoritesViewModel.removeFavorite(bookId)
favoritesViewModel.updateUserRating(bookId, 4.5)

Updating Username

// In any composable with UserProfileViewModel injected
userProfileViewModel.updateUsername("John Doe")

Observing Data

All data is exposed as StateFlow, making it easy to observe in Composables:

val favoriteBooks by favoritesViewModel.favoriteBooks.collectAsState()
val feedbackList by feedbackViewModel.feedbackList.collectAsState()
val username by userProfileViewModel.username.collectAsState()

Benefits

  1. Persistence: All data survives app restarts
  2. Offline Support: Works without internet connection
  3. Reactive: UI automatically updates when data changes (Flow/StateFlow)
  4. Type-Safe: Kotlin-first approach with compile-time safety
  5. Performance: Efficient queries and lazy loading
  6. Redundancy: User data saved to multiple locations (Realm, SharedPreferences, Firebase)

Data Storage Locations

User Profile

  • Primary: Realm DB (local, fast access)
  • Backup: Encrypted SharedPreferences
  • Cloud: Firebase Firestore (if user is logged in)

Favorites

  • Storage: Realm DB only
  • Synced: Automatically across all screens via singleton ViewModel

Feedback

  • Storage: Realm DB only
  • Accessible: Via ViewFeedbackScreen

Future Enhancements

Potential improvements:

  1. Add Firebase sync for favorites (cross-device sync)
  2. Export feedback to CSV/JSON
  3. Add statistics dashboard for reading habits
  4. Implement data migration from Room to Realm (if needed)
  5. Add search/filter for feedback history
  6. Backup/restore functionality

Testing

To verify the implementation:

  1. Add books to favorites → Close app → Reopen → Favorites should persist
  2. Submit feedback → Navigate to ViewFeedbackScreen → See saved feedback
  3. Update username → Close app → Reopen → Username should persist

Database Location

The Realm database file is stored at:

/data/data/com.example.reader/files/reader_app.realm

You can inspect it using Realm Studio for debugging.

Notes

  • Realm operations are performed on background threads (suspend functions)
  • UI updates happen automatically via Flow
  • Database is initialized once at app startup
  • All ViewModels use the same singleton RealmRepository instance
  • Favorites ViewModel is also a singleton to maintain state across navigation