This article is the second part of the Flutter tutorial series. During the series, you will learn how to build cross-platform apps without worrying about the backend.
In this article, I will show you how you can make a secure chat application by introducing authorization to the basic chat app that we created previously.
We will store the chat data on Supabase.
Supabase utilizes the built in authorization mechanism of PostgreSQL called Row Level Security or RLS to prevent unauthorized access from accessing or writing data to your database.
RLS allows developers to define row-by-row conditions that evaluate to either true or false to either allow the access or deny it.
We will take a look at more specific examples of authorization using RLS throughout this article.
What we created in the previous article#
Before we jump in, let's go over what we built in the previous article, because we will be building on top of it. If you have not gone through it, I recommend you to go check it out.
In the previous article, we created a basic real-time chat application. Users will register or sign in using an email address and password. Once they are signed in, they are taken to a chat page, where they can view and send messages to everyone in the app. There are no Chat rooms, and everyone's messages were sent to the same chat room.
You can also find a complete code example here to follow along.
The app will allow us to have 1 on 1 chat with other users in the app. To enable this, we will introduce a new rooms page. The rooms page serves two purposes here, one is to initiate a conversation with other users, and the other is to display existing chat rooms. At the top of the app, we see a list of other users' icons. A user can tap the icon to start a 1 on 1 conversation. Below the icons, there is a list of rooms that the user is a part of.
Install additional dependencies#
We will install flutter_bloc for state management. Introducing a state management solution will allow us to handle the shared message and profile data efficiently between the rooms page and the chats page. We can use any state management solution for this, but we are going with bloc in this example. Add the following in your pubspec.yaml file to install flutter_bloc in your app.
Modifying the table schema#
Since the app has evolved, we also need to update our table schema. In order to store rooms data, we will add a rooms table. We will also modify the messages table to add a foreign key constraint to the rooms table so that we can tell which message belongs to which room.
We will also introduce a create_new_room function, which is a database function that handles chat room creation. It knows to create a new room if a chat room with the two users does not exist yet, or to just return the room ID if it already exists.
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-- *** Table definitions ***
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create table if not exists public.rooms (
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id uuid not null primary key default gen_random_uuid(),
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created_at timestamp with time zone default timezone('utc' :: text, now()) not null
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);
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comment on table public.rooms is 'Holds chat rooms';
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create table if not exists public.room_participants (
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profile_id uuid references public.profiles(id) on delete cascade not null,
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room_id uuid references public.rooms(id) on delete cascade not null,
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created_at timestamp with time zone default timezone('utc' :: text, now()) not null,
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primary key (profile_id, room_id)
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);
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comment on table public.room_participants is 'Relational table of users and rooms.';
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alter table public.messages
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add column room_id uuid references public.rooms(id) on delete cascade not null;
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-- *** Add tables to the publication to enable realtime ***
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alter publication supabase_realtime add table public.room_participants;
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-- Creates a new room with the user and another user in it.
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-- Will return the room_id of the created room
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-- Will return a room_id if there were already a room with those participants
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create or replace function create_new_room(other_user_id uuid) returns uuid as $$
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declare
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new_room_id uuid;
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begin
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-- Check if room with both participants already exist
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with rooms_with_profiles as (
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select room_id, array_agg(profile_id) as participants
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from room_participants
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group by room_id
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)
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select room_id
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into new_room_id
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from rooms_with_profiles
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where create_new_room.other_user_id=any(participants)
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and auth.uid()=any(participants);
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if not found then
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-- Create a new room
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insert into public.rooms default values
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returning id into new_room_id;
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-- Insert the caller user into the new room
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insert into public.room_participants (profile_id, room_id)
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values (auth.uid(), new_room_id);
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-- Insert the other_user user into the new room
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insert into public.room_participants (profile_id, room_id)
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values (other_user_id, new_room_id);
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end if;
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return new_room_id;
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end
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$$ language plpgsql security definer;
Setup deep links#
Something we skipped in the previous article was sending confirmation emails to users when they signup. Since today is about security, let's properly send confirmation emails to people who signup.
When we send confirmation emails, the users need to be brought back to the app somehow.
Since supabase_flutter has a mechanism to detect and handle deep links, we will register a io.supabase.chat://login as our deep link for the app and bring the users back after confirming their email address.
For iOS we edit the info.plist file to register the deep link.
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<!-- ... other tags -->
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<plist>
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<dict>
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<!-- ... other tags -->
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<!-- Add this array for Deep Links -->
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<key>CFBundleURLTypes</key>
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<array>
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<dict>
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<key>CFBundleTypeRole</key>
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<string>Editor</string>
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<key>CFBundleURLSchemes</key>
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<array>
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<string>io.supabase.chat</string>
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</array>
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</dict>
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</array>
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<!-- ... other tags -->
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</dict>
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</plist>
For Android we edit the AndroidManifest.xml to register the deep link.
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<manifest ...>
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<!-- ... other tags -->
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<application ...>
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<activity ...>
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<!-- ... other tags -->
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<!-- Add this intent-filter for Deep Links -->
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<intent-filter>
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<action android:name="android.intent.action.VIEW" />
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<category android:name="android.intent.category.DEFAULT" />
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<category android:name="android.intent.category.BROWSABLE" />
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<!-- Accepts URIs that begin with YOUR_SCHEME://YOUR_HOST -->
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<data
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android:scheme="io.supabase.chat"
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android:host="login" />
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</intent-filter>
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</activity>
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</application>
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</manifest>
We also need to set the deep link in our Supabase dashboard. Go to Authentication > URL Configuration in your dashboard and add io.supabase.chat://login as one of the redirect URLs.
And that is it for deep link configuration.
Building out the main application#
Step1: Create rooms page#
The rooms page will load two types of data, recently added users and a list of rooms that the user belongs to. We will be using bloc to load these two types of data and display them on the rooms page.
Let's start out by creating states for the rooms page.
The rooms page would have four different states, loading, loaded, empty, and error. We will display different UI on the rooms page depending on what state it is.
Satrt by defining the Room model. Create a lib/models/room.dart file and add the following code.
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import 'package:my_chat_app/models/message.dart';
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class Room {
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Room({
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required this.id,
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required this.createdAt,
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required this.otherUserId,
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this.lastMessage,
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});
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/// ID of the room
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final String id;
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/// Date and time when the room was created
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final DateTime createdAt;
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/// ID of the user who the user is talking to
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final String otherUserId;
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/// Latest message submitted in the room
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final Message? lastMessage;
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Map<String, dynamic> toMap() {
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return {
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'id': id,
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'createdAt': createdAt.millisecondsSinceEpoch,
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};
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}
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/// Creates a room object from room_participants table
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Room.fromRoomParticipants(Map<String, dynamic> map)
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: id = map['room_id'],
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otherUserId = map['profile_id'],
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createdAt = DateTime.parse(map['created_at']),
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lastMessage = null;
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Room copyWith({
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String? id,
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DateTime? createdAt,
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String? otherUserId,
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Message? lastMessage,
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}) {
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return Room(
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id: id ?? this.id,
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createdAt: createdAt ?? this.createdAt,
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otherUserId: otherUserId ?? this.otherUserId,
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lastMessage: lastMessage ?? this.lastMessage,
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);
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}
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}
We will proceed with defining the states for the rooms page. Create lib/cubit/rooms/rooms_state.dart file and paste the following code.
You may see some errors, but we will take care of them in the next step.
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part of 'rooms_cubit.dart';
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@immutable
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abstract class RoomState {}
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class RoomsLoading extends RoomState {}
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class RoomsLoaded extends RoomState {
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final List<Profile> newUsers;
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final List<Room> rooms;
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RoomsLoaded({
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required this.rooms,
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required this.newUsers,
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});
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}
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class RoomsEmpty extends RoomState {
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final List<Profile> newUsers;
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RoomsEmpty({required this.newUsers});
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}
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class RoomsError extends RoomState {
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final String message;
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RoomsError(this.message);
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}
Now that we have the states defined, we will create rooms_cubit.
A cubit is a class within the flutter_bloc library where we will make requests to Supabase to get the data and transform them into states and emit them to the UI widgets.
Let's create a lib/cubit/rooms/rooms_cubit.dart file and complete the cubit.
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import 'dart:async';
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import 'package:flutter/material.dart';
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import 'package:flutter_bloc/flutter_bloc.dart';
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import 'package:my_chat_app/cubits/profiles/profiles_cubit.dart';
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import 'package:my_chat_app/models/profile.dart';
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import 'package:my_chat_app/models/message.dart';
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import 'package:my_chat_app/models/room.dart';
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import 'package:my_chat_app/utils/constants.dart';
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part 'rooms_state.dart';
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class RoomCubit extends Cubit<RoomState> {
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RoomCubit() : super(RoomsLoading());
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final Map<String, StreamSubscription<Message?>>
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_messageSubscriptions = {};
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late final String _myUserId;
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/// List of new users of the app for the user to start talking to
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late final List<Profile> _newUsers;
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/// List of rooms
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List<Room> _rooms = [];
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StreamSubscription<List<Map<String, dynamic>>>?
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_rawRoomsSubscription;
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bool _haveCalledGetRooms = false;
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Future<void> initializeRooms(BuildContext context) async {
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if (_haveCalledGetRooms) {
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return;
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}
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_haveCalledGetRooms = true;
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_myUserId = supabase.auth.currentUser!.id;
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late final List data;
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try {
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data = await supabase
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.from('profiles')
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.select()
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.not('id', 'eq', _myUserId)
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.order('created_at')
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.limit(12);
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} catch (_) {
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emit(RoomsError('Error loading new users'));
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}
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final rows = List<Map<String, dynamic>>.from(data);
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_newUsers = rows.map(Profile.fromMap).toList();
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/// Get realtime updates on rooms that the user is in
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_rawRoomsSubscription =
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supabase.from('room_participants').stream(
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primaryKey: ['room_id', 'profile_id'],
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).listen((participantMaps) async {
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if (participantMaps.isEmpty) {
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emit(RoomsEmpty(newUsers: _newUsers));
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return;
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}
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_rooms = participantMaps
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.map(Room.fromRoomParticipants)
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.where((room) => room.otherUserId != _myUserId)
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.toList();
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for (final room in _rooms) {
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_getNewestMessage(
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context: context, roomId: room.id);
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BlocProvider.of<ProfilesCubit>(context)
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.getProfile(room.otherUserId);
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}
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emit(RoomsLoaded(
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newUsers: _newUsers,
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rooms: _rooms,
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));
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}, onError: (error) {
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emit(RoomsError('Error loading rooms'));
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});
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}
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// Setup listeners to listen to the most recent message in each room
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void _getNewestMessage({
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required BuildContext context,
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required String roomId,
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}) {
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_messageSubscriptions[roomId] = supabase
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.from('messages')
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.stream(primaryKey: ['id'])
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.eq('room_id', roomId)
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.order('created_at')
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.limit(1)
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.map<Message?>(
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(data) => data.isEmpty
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? null
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: Message.fromMap(
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map: data.first,
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myUserId: _myUserId,
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),
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)
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.listen((message) {
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final index = _rooms
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.indexWhere((room) => room.id == roomId);
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_rooms[index] =
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_rooms[index].copyWith(lastMessage: message);
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_rooms.sort((a, b) {
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/// Sort according to the last message
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/// Use the room createdAt when last message is not available
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final aTimeStamp = a.lastMessage != null
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? a.lastMessage!.createdAt
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: a.createdAt;
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final bTimeStamp = b.lastMessage != null
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? b.lastMessage!.createdAt
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: b.createdAt;
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return bTimeStamp.compareTo(aTimeStamp);
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});
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if (!isClosed) {
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emit(RoomsLoaded(
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newUsers: _newUsers,
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rooms: _rooms,
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));
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}
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});
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}
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/// Creates or returns an existing roomID of both participants
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Future<String> createRoom(String otherUserId) async {
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final data = await supabase.rpc('create_new_room',
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params: {'other_user_id': otherUserId});
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emit(RoomsLoaded(rooms: _rooms, newUsers: _newUsers));
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return data as String;
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}
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@override
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Future<void> close() {
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_rawRoomsSubscription?.cancel();
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return super.close();
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}
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}
Now that we have the states and cubit to power our rooms page, it's time to create the RoomsPage.
We have two list views, one horizontal list view to display other users, and one vertical list views with list tiles representing each room that the user is a part of.
We will create a lib/pages/rooms_page.dart file with the following content.
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import 'package:flutter/material.dart';
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import 'package:flutter_bloc/flutter_bloc.dart';
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import 'package:my_chat_app/cubits/profiles/profiles_cubit.dart';
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import 'package:my_chat_app/cubits/rooms/rooms_cubit.dart';
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import 'package:my_chat_app/models/profile.dart';
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import 'package:my_chat_app/pages/chat_page.dart';
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import 'package:my_chat_app/pages/register_page.dart';
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import 'package:my_chat_app/utils/constants.dart';
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import 'package:timeago/timeago.dart';
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/// Displays the list of chat threads
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class RoomsPage extends StatelessWidget {
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const RoomsPage({Key? key}) : super(key: key);
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static Route<void> route() {
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return MaterialPageRoute(
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builder: (context) => BlocProvider<RoomCubit>(
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create: (context) =>
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RoomCubit()..initializeRooms(context),
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child: const RoomsPage(),
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),
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);
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}
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@override
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Widget build(BuildContext context) {
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return Scaffold(
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appBar: AppBar(
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title: const Text('Rooms'),
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actions: [
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TextButton(
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onPressed: () async {
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await supabase.auth.signOut();
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Navigator.of(context).pushAndRemoveUntil(
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RegisterPage.route(),
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(route) => false,
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);
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},
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child: const Text('Logout'),
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),
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],
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),
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body: BlocBuilder<RoomCubit, RoomState>(
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builder: (context, state) {
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if (state is RoomsLoading) {
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return preloader;
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} else if (state is RoomsLoaded) {
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final newUsers = state.newUsers;
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final rooms = state.rooms;
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return BlocBuilder<ProfilesCubit,
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ProfilesState>(
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builder: (context, state) {
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if (state is ProfilesLoaded) {
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final profiles = state.profiles;
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return Column(
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children: [
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_NewUsers(newUsers: newUsers),
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Expanded(
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child: ListView.builder(
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itemCount: rooms.length,
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itemBuilder: (context, index) {
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final room = rooms[index];
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final otherUser =
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profiles[room.otherUserId];
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return ListTile(
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onTap: () =>
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Navigator.of(context)
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.push(ChatPage.route(
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room.id)),
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leading: CircleAvatar(
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child: otherUser == null
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? preloader
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: Text(otherUser
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.username
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.substring(0, 2)),
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),
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title: Text(otherUser == null
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? 'Loading...'
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: otherUser.username),
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subtitle: room.lastMessage !=
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null
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? Text(
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room.lastMessage!
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.content,
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maxLines: 1,
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overflow: TextOverflow
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.ellipsis,
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)
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: const Text(
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'Room created'),
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trailing: Text(format(
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room.lastMessage
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?.createdAt ??
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room.createdAt,
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locale: 'en_short')),
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);
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},
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),
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),
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],
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);
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} else {
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return preloader;
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}
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},
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);
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} else if (state is RoomsEmpty) {
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final newUsers = state.newUsers;
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return Column(
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children: [
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_NewUsers(newUsers: newUsers),
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const Expanded(
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child: Center(
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child: Text(
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'Start a chat by tapping on available users'),
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),
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),
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],
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);
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} else if (state is RoomsError) {
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return Center(child: Text(state.message));
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