Initializing SDK Clients

Once your Chat Client is fully synchronized at client startup:

• The client is subscribed to events for all User Channels.
• The Messages and Members collections are available for querying.
• The only initially subscribed User in the system is that of the local user, which will never be automatically unsubscribed.

No previously existing Messages are fetched for the client on load. These will be loaded when you call the getMessages method to fetch messages on demand. Messages are then cached and updated after loading.

You receive feedback on client startup in two ways:

• You will receive an asynchronous callback from the create client method when the client has been successfully created and is being synchronized.
• You will receive an event to the client's listener or delegate via the synchronizationStatusUpdated method with a value of StatusCompleted. This is your indication the client is ready for business, and all User Channels have been obtained and subscribed to.

The JavaScript client will retrieve the list of Subscribed Channels that a User is a Member of (or has been invited to) once that user logs into the client.

Some additional details on the JavaScript SDK behavior:

• It will subscribe to notifications for changes to the Subscribed Channel list itself
• It will subscribe to events from each Subscribed Channel in the list
• It will retrieve the FriendlyName , UniqueName, and Attributes for each Subscribed Channel in the list
• It will not retrieve any Messages for individual Channels
• It will retrieve Member lists for Channels
• It will not retrieve nor subscribe to Users linked to Members of Subscribed Channels
• It will retrieve a currently logged in User object and subscribe to this User's events

To load Messages for a Subscribed Channel and subscribe to other Channel-level events you will need to load individual Channels manually. More information on this can be found in the Channels and Messages guide.

It is important to know when the SDK Client has completed its initialization and is ready for use. Once the client is connected, you can configure all your listeners, event handlers, and other logic.

This manifests slightly differently for each SDK as detailed below:

The Chat Client is instantiated in one of two ways:

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Twilio.Chat.Client.create(token).then(client => {
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    // Use client
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});

Or asynchronously, waiting for the result:

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let client = await Twilio.Chat.Client.create(token);
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// Use client

First, we initialize the Chat Client. Here we provide an initial Access Token:

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 NSString *token = <token goes here>;
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    __weak typeof(self) weakSelf = self;
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    [TwilioChatClient chatClientWithToken:token
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                                    properties:nil
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                                    delegate:<delegate>
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                                    completion:^(TCHResult *result, TwilioChatClient *chatClient) { 
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                                            weakSelf.client = chatClient;
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                                     ... }];

The iOS Chat SDK then provides a TCHClientSynchronizationStatus delegate callback:

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    - (void)chatClient:(TwilioChatClient *)client
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    synchronizationStatusUpdated:(TCHClientSynchronizationStatus)status {
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        if (status == TCHClientSynchronizationStatusCompleted) {
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            // Client is now ready for business
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        }
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    }

The Android Chat SDK provides a Listener Interface which you must implement to check the init status and completion of the SDK client.

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    ChatClient.Properties props = new ChatClient.Properties.Builder()
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        .createProperties();
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    ChatClient.create(context.getApplicationContext(),
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      accessToken,
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      props,
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      new CallbackListener<ChatClient>() {
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        @Override
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        public void onSuccess(final ChatClient client) {
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          // save client for future use here
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          client.setListener(new ChatClientListener() {
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            @Override
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            public void onClientSynchronization(ChatClient.SynchronizationStatus status) {
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              if (status == ChatClient.SynchronizationStatus.COMPLETED) {
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                // Client is now ready for business, start working
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              }
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            }
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          });
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        }
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      });

Before we get too much deeper into showing how to get your users chatting, it's important to know where to look for logs and additional information if you need it. We have a guide about Error Handling and Diagnostics and Programmable Chat you may find helpful as you build your Chat integration.

All Chat SDK clients need a valid Access Token to be able to authenticate and interact with the Chat Service. The Access Token is generated on your server - you can learn more about how to do that in the Access Token guide.

The Access Token returned by your backend must be used when instantiating the SDK Client. You will pass the Token string directly to the SDK Client constructor method.

The SDK also provides a method to update the Access Token, which is used when you need to update the Access Token before expiration. Please see the Creating Access Tokens guide for more information.

Next: Creating Access Tokens