SDK Migration Guide - iOS 1.0

Twilio Programmable Chat 1.0 brings additional controls on data synchronization to enhance performance as well as many other improvements. This guide will help you migrate your existing Chat applications to the new strategies supported by release 1.0.

Client and Channel delegates have been expanded to indicate what parts of the object have been updated, allowing you to tailor UI updates to the information that has changed.

Users are no longer implicitly subscribed to improve performance on large instances. You can subscribe up to a maximum number of users at once after which your least recently used User will be unsubscribed. Using either subscribed Users or User Descriptors appropriately is key to the performance of your application:

• Subscribed Users will immediately reflect changes made on other clients, such as Friendly Name and Attributes and will also have the most up-to-date reachability and online status information. Subscribed Users are best for live display of messages or recently contacted Users by the client.
• User Descriptors are a snapshot in time of that user's status in the system. These snapshot objects are ideal for temporary lists of users within your user interface or for visualizing large numbers of users on a Channel where constant data synchronization is not key.

The notifications registration process has been streamlined, reflecting success of subscribing to push notifications in a callback rather than the separate delegate methods previously exposed.

Client initialization has been simplified to reflect most users typical usage of the system. All user channels (channels for which the current user is joined to or an owner of) will be subscribed to from client startup but only the members roster will be synchronized initially. This keeps client startup fast while still reflecting the latest activity immediately to the client. This removes the requirement to manually call synchronizeWithCompletion: on channel objects to begin utilizing them.

Creation of the Chat client is now asynchronous and the client object is returned to you as part of a new completion block. This change reflects the possibility that client creation may fail due to issues with the provided access token. Client creation with chatClientWithToken:properties:delegate: is now replaced with chatClientWithToken:properties:delegate:completion: and returns nil instead of a client object. The client object, once the completion is called, is ready for use.

The TwilioChatClientProperties object provided during client creation has two fewer properties:

synchronizationStrategy has been deprecated. All user channels are implicitly synchronized in Chat 1.0 so that events for Channels the user is joined to will be delivered from client initialization.

To ensure the impact on clients for this change are manageable, Chat will no longer implicitly load a pre-determined list of messages (now deprecated initialMessageCount property also on this object) nor will it synchronize the UserInfo objects for Channel's Members. These objects incur frequent updates and can incur additional burden for clients unnecessarily. If you are relying on initialMessageCount in your implementation, we recommend you consider fetching messages on demand as the user displays the UI for the channel. If having a some messages initially is key to your use case, you may iterate through the subscribedChannels: once the client is fully synchronized to seed the local cache with a history of messages.

updateToken: has transitioned to updateToken:completion: which will provide an indication of success for the token update operation.

(de)registerWithToken: has been renamed to (de)registerWithNotificationToken:completion: to differentiate notification tokens from access tokens and the completion block will indicate an initial reflection of the success of the request and chatClientToastSubscribed: and chatClient:toastRegistrationFailedWithError: have been retired. handleNotification: has been expanded to handleNotification:completion: to indicate if the notification was able to be processed by the chat client.

The chatClient:toastReceivedOnChannel:message: delegate method has been changed to chatClient:notificationNewMessageReceivedForChannelSid:messageIndex: to better reflect both the nature of the notification and the fact the channel or message in question may not be synchronized to the client at the time the delegate is called.

Each changed delegate callback on both the Client and Channel delegates (Channel, Message, Member and User) includes an updated parameter which will give you information as to what on the object changed and has removed the Changed portion of its name.

The chatClient:connectionStateChanged: method has been renamed to chatClient:connectionStateUpdated: .

The chatClient:synchronizationStatusChanged: method has been renamed to chatClient:synchronizationStatusUpdated: .

The chatClient:channel:synchronizationStatusChanged: delegate method has been deprecated. You can now determine if the synchronization status has changed for a channel through the expanded chatClient:channel:updated: delegate callback, checking for a TCHChannelUpdate value of TCHChannelUpdateSynchronizationStatus .

The userInfo property has been renamed to user to reflect the splitting of TCHUserInfo to distinct TCHUser and TCHUserDescriptor objects. Unlike User objects associated with Members, the User whose client this is will always be in a subscribed state (more on this further in the document.) You can access your client's TCHUsers using the users accessor on the TwilioChatClient object.

TCHUserInfo has been deprecated and replaced with two distinct objects, TCHUser and TCHUserDescriptor. Similar to TCHChannelDescriptor objects, a TCHUserDescriptor represents a snapshot of data in time that should be utilized directly after obtaining it but not retained since it will not be updated with new data over time.

TCHUser objects add a new concept to Programmable Chat, subscriptions. A Programmable Chat primitive is subscribed if it will receive updates from the server. TCHChannel objects at this time are always subscribed, and TCHChannelDescriptor objects are not. Similarly, TCHUserDescriptor objects are not subscribed but a TCHUser object may or may not be subscribed. When a TCHUser is initially subscribed to on the client, you will receive the chatClient:userSubscribed: delegate callback.

When you first obtain a TCHUser object, it will be subscribed but there is a maximum number of TCHUser objects which may be subscribed at a time in the Programmable Chat client. Once this limit is exceeded, the least recently subscribed TCHUser object in memory will be unsubscribed. Several things happen when this occurs:

• The new chatClient:userUnsubscribed: delegate method will be called to let you know the object is no longer receiving updates
• The Chat client will no longer maintain a strong reference to the TCHUser object, causing it to be released unless you were holding it strongly
• The isSubscribed accessor will start to return a false value if you still have a reference to the TCHUser object
• Attempting to read data from the unsubscribed TCHUser object will return nil for it values
• The online and notifiable Boolean values on an unsubscribed TCHUser will return NO. This reflects a lack of information of the user's current status similar to the nil values returned for other parameters.
• If you subscribe the TCHUser again using the methods described below, a new TCHUser object will be generated

The number of Users you can concurrently subscribe to in a given instance of the Chat client is large enough that many implementation of Chat will not be affected by User objects being unsubscribed. This is something you should provide for in your code though, and ensure you are using TCHUser objects when consistently updated representation of users is important and TCHUserDescriptors when displaying a temporary UI such as a membership list.

The new TCHUserDescriptor object has all of the accessors of the deprecated TCHUserInfo object but none of the setters. It also has an synchronous method subscribeWithCompletion: that will return a subscribed TCHUser object.

The new TCHUser object has the full functionality of the old TCHUserInfo object along with a isSubscribed property which should be checked to see if a TCHUser object is still subscribed. Also, the accessors on this object may return nil if the TCHUser object has been unsubscribed. There is an unsubscribe method on this object which will remove the TCHUser object from the subscription pool explicitly if you no longer need updates for it at this time.

A new TCHUsers class exists, accessible from the client instance with the users method. This class is one way to access TCHUser and TCHUserDescriptor objects. Methods this class provides include:

• userDescriptorsForChannel:completion: is a convenience method to retrieve TCHUserDescriptor objects for an entire Channel's membership with a single asynchronous call. You always have the option to obtain TCHUserDescriptor objects individually for a channel's Member but for a large number of Members this method is faster. The return will be a list of ephemeral UserDescriptor objects
• userDescriptorWithIdentity:completion: provides a TCHUserDescriptor instance for the specified identity
• subscribedUserWithIdentity:completion: retrieves and subscribes the TCHUser object for the specified identity. If the user object is already subscribed, this will be an instance to that object otherwise a new subscription will be created
• subscribedUsers synchronously returns a list of currently subscribed TCHUser objects TCHChannels Changes

There is a new synchronous method, subscribedChannels which will give you the list of currently synchronized channels. This method replaces the deprecated userChannelsWithCompletion: method. The publicChannelsWithCompletion: method has been renamed to publicChannelDescriptorsWithCompletion: for clarity on its returned objects and a new method, userChannelDescriptorsWithCompletion: has been added.

synchronizeWithCompletion: has been deprecated since TCHChannel objects are now always synchronized once loaded.

All delegate methods supported by the TCHChannelDelegate protocol have updated variables passed for methods indicating objects have changed, describing the nature of the change.

The membersWithCompletion: accessor on the TCHMembers object for a channel will now page results, previously this always returned a single page regardless of Channel membership size. It is also important to note that the first call to this method will need to bring down the channel's membership list - it is subscribed implicitly when the channel is obtained but not populated with existing Members.

userInfo is replaced with a new identity property which will provide the string identity for the Member. There are also two convenience methods on this class, userDescriptorWithCompletion: and subscribedUserWithCompletion: to obtain a TCHUserDescriptor and subscribed TCHUser object respectively.

Two new properties exist, resultCode and resultText to give more context to operation responses. The isSuccessful Boolean check remains the best way to tell quickly if an operation succeeded.