Amazon IVS Chat Client Messaging SDK: React Native Tutorial Part 2: Messages and Events
This second (and last) part of the tutorial is broken up into several sections:
Note: In some cases, code examples for JavaScript and TypeScript are identical, so they are combined.
Prerequisite
Be sure you have completed Part 1 of this tutorial, Chat Rooms.
Subscribe to Chat Message Events
The ChatRoom instance uses events to communicate when events occur in a chat
room. To start implementing the chat experience, you need to show your users when others send
a message in the room to which they're connected.
Here, you subscribe to chat message events. Later, we’ll show you how to update a message list you create, which updates with every message/event.
In your App, inside the useEffect hook, subscribe to all message
events:
TypeScript/JavaScript:
// App.tsx / App.jsx useEffect(() => { // ... const unsubscribeOnMessageReceived = room.addListener('message', (message) => {}); return () => { // ... unsubscribeOnMessageReceived(); }; }, []);
Show Received Messages
Receiving messages is a core part of the chat experience. Using the Chat JS SDK, you can set up your code to easily receive events from other users connected to a chat room.
Later, we’ll show you how to perform actions in a chat room that leverage the components you create here.
In your App, define a state named messages with a
ChatMessage array type named messages:
Next, in the message listener function, append message to the
messages array:
TypeScript/JavaScript:
// App.tsx / App.jsx // ... const unsubscribeOnMessageReceived = room.addListener('message', (message) => { setMessages((msgs) => [...msgs, message]); }); // ...
Below we step through the tasks to show received messages:
Creating a Message Component
The Message component is responsible for rendering the contents of a
message received by your chat room. In this section, you create a messages component for
rendering individual chat messages in the App.
Create a new file in the src directory and name it Message.
Pass in the ChatMessage type for this component, and pass the
content string from ChatMessage properties to display message
text received from chat-room message listeners. In the Project Navigator, go to
Message.
Tip: Use this component to store different properties that you want to render in your message rows; for example, avatar URLs, user names, and timestamps of when the message was sent.
Recognizing Messages Sent by the Current User
To recognize the message sent by the current user, we modify the code and create a React
context for storing the userId of the current user.
Create a new file in the src directory and name it
UserContext:
Note: Here we used the useState hook to store the userId
value. In the future you can use setUserId to change user context or for login
purposes.
Next, replace userId in the first parameter passed to
tokenProvider, using the previously created context. Make sure you add the
SEND_MESSAGE capability to your token provider, as specified below; it is
required to send messages.:
In your Message component, use the UserContext created before,
declare the isMine variable, match the sender’s userId with the
userId from the context, and apply different styles of messages for the
current user.
Rendering a List of Chat Messages
Now list messages using FlatList and Message component:
All the puzzle pieces are now in place for your App to start rendering
messages received by your chat room. Continue below to see how to perform actions in a chat
room that leverage the components you have created.
Perform Actions in a Chat Room
Sending messages and performing moderator actions are some of the primary ways you interact with a chat room. Here you will learn how to use various chat request objects to perform common actions in Chatterbox, such as sending a message, deleting a message, and disconnecting other users.
All actions in a chat room follow a common pattern: for every action you perform in a chat room, there is a corresponding request object. For each request there is a corresponding response object that you receive on request confirmation.
As long as your users are granted the correct capabilities when you create a chat token, they can successfully perform the corresponding action(s) using the request objects to see what requests you can perform in a chat room.
Below, we explain how to send a message and delete a message.
Sending a Message
The SendMessageRequest class enables sending messages in a chat room. Here,
you modify your App to send a message request using the component you created
in Create a Message Input (in Part 1
of this tutorial).
To start, define a new boolean property named isSending with the
useState hook. Use this new property to toggle the disabled state of your
button element, using the isSendDisabled constant. In the event
handler for your SendButton, clear the value for messageToSend and
set isSending to true.
Since you will be making an API call from this button, adding
the isSending boolean helps prevent multiple API calls from occuring at the
same time, by disabling user interactions on your SendButton until the
request is complete.
Note: Sending messages works only if you added the SEND_MESSAGE capability
to your token provider, as covered above in Recognizing Messages Sent by the Current User.
TypeScript/JavaScript:
// App.tsx / App.jsx // ... const [isSending, setIsSending] = useState(false); // ... const onMessageSend = () => { setIsSending(true); setMessageToSend(''); }; // ... const isSendDisabled = connectionState !== 'connected' || isSending; // ...
Prepare the request by creating a new SendMessageRequest instance, passing
message content to the constructor. After setting the isSending and
messageToSend states, call the sendMessage method, which sends
the request to the chat room. Finally, clear the isSending flag on receiving
confirmation or rejection of the request.
TypeScript/JavaScript:
// App.tsx / App.jsx // ... import { ChatRoom, ConnectionState, SendMessageRequest } from 'amazon-ivs-chat-messaging' // ... const onMessageSend = async () => { const request = new SendMessageRequest(messageToSend); setIsSending(true); setMessageToSend(''); try { const response = await room.sendMessage(request); } catch (e) { console.log(e); // handle the chat error here... } finally { setIsSending(false); } }; // ...
Give Chatterbox a run: try sending a message by drafting one with your
MessageBar and tapping your SendButton. You should see your sent
message rendered within the MessageList that you created earlier.
Deleting a Message
To delete a message from a chat room, you need to have the proper capability.
Capabilities are granted during the initialization of the chat token that you use when
authenticating to a chat room. For the purposes of this section, the ServerApp
from Set Up a Local
Authentication/Authorization Server (in Part 1 of this tutorial) lets you specify
moderator capabilities. This is done in your app using the tokenProvider object
that you created in Build a Token
Provider (also in Part 1).
Here you modify your Message by adding a function to delete the
message.
First, open the App.tsx and add the DELETE_MESSAGE capability.
(capabilities is the second parameter of your tokenProvider
function.)
Note: This is how your ServerApp informs the IVS Chat APIs that the user
being associated with the resulting chat token can delete messages in a chat room. In a
real-world situation you probably will have more complex backend logic to manage user
capabilities in your server app's infrastructure.
TypeScript/JavaScript:
// App.tsx / App.jsx // ... const [room] = useState(() => new ChatRoom({ regionOrUrl: process.env.REGION, tokenProvider: () => tokenProvider(userId, ['SEND_MESSAGE', 'DELETE_MESSAGE']), }), ); // ...
In the next steps, you update your Message to display a delete
button.
Define a new function called onDelete that accepts a string as one of its
parameters and returns Promise. For the string parameter, pass in your
component message ID.
Next, you update your renderItem to reflect the latest changes to your
FlatList component.
In App, define a function named handleDeleteMessage and pass
it to the MessageList onDelete property:
Prepare a request by creating a new instance of DeleteMessageRequest,
passing the relevant message ID to the constructor parameter, and call
deleteMessage that accepts the prepared request above:
Next, you update your messages state to reflect a new list of messages that
omits the message you just deleted.
In the useEffect hook, listen for the messageDelete event and
update your messages state array by deleting the message with a matching ID to
the message parameter.
Note: The messageDelete event might be raised for messages being deleted by
the current user or any other user in the room. Handling it in the event handler (instead of
next to the deleteMessage request) allows you to unify delete-message
handling.
TypeScript/JavaScript:
// App.tsx / App.jsx // ... const unsubscribeOnMessageDeleted = room.addListener('messageDelete', (deleteMessageEvent) => { setMessages((prev) => prev.filter((message) => message.id !== deleteMessageEvent.id)); }); return () => { // ... unsubscribeOnMessageDeleted(); }; // ...
You are now able to delete users from a chat room in your chat app.
Next Steps
As an experiment, try implementing other actions in a room like disconnecting another user.
