Data components

Data components are responsible for managing data between the UI Components and the persistence layer. They also interact with the PubNub service by sending and receiving messages and signals.

Available components include:

• Channel Data
• Member Data
• Message Data

Overview

PubNub Chat Components for Android utilize several layers of configurable data to drive the functionality found in the UI Components. The goal of the data layer is to provide a simple and robust foundation that can be used across any chat implementation. The two main forms of data used by the components are persistent and network objects.

Persistent data

All the data is stored as entities in a local database using Room, an abstraction layer over SQLite. Room provides the following benefits:

• Compile-time verification of SQL queries.
• Convenience annotations that minimize repetitive and error-prone boilerplate code.
• Streamlined database migration paths.

You can find the default implementation of the database in ChatProvider. It contains data entities, data access objects, and database implementation. Additionally, ChatProvider uses the repository design pattern that allows for separation of concerns by abstracting the data persistence logic.

To learn more about Room, refer to the official Android docs.

Network data

Network objects are most commonly used when interacting with PubNub APIs. Those objects exist only at the network layer and need to be converted with Data Mappers to be used in the application.

UI data

The UI Components don't use persistent or network data but extra UI data objects are created for them instead. These UI data objects contain only user-readable information. For example, to display a timetoken, it must be converted to a date string first.

Data Mappers

The role of Data Mappers is to convert one data type to another to allow developers to swap between Persistent, Network, and UI data objects. For example, when the PNMessageResult is received by MessageService, the data is converted to DBMessage and stored in the database. Similarly to the previous example, when the user sends a message, the MessageUi.Data object is converted to DBMessage and stored in the local database. At the same time, the object is converted to NetworkMessage and published in PubNub.

View models

The ViewModel class is designed to store and manage UI-related data by communicating with services and repositories.

For more information on view models, refer to the official Android docs.

Services

The role of services is to communicate with PubNub APIs, add, get, or update objects and store them using local repositories. The default implementation of services exists in the ChatProvider composition tree.

Data flow

The typical data flow through the components revolves around storing incoming data in the Room database instance and updating that data automatically in UI Components if the data matches the UI Components population query.

1. The PubNub APIs and events return network data that can be stored directly in the Room database using the repositories declared in ChatProvider.

2. The UI Components use specific view models to connect with the database (persistent data) through repositories and Data Access Object instances. If the returned type of the ViewModel method is declared as Flow, it automatically updates the component's data source if the new matching data is added, updated, or removed.

3. The UI Components provide actions that can be configured to call PubNub APIs through DataProvider or update existing objects and store the result.

Channel

A channel is commonly viewed as a collection of associated users with a specific purpose or goal. A channel could be created for direct communication between two or more users, a group of users, or other use-case specific scenarios.

Persistent data

The default Persistent Object Model inside the Chat Components defines an Entity named DBChannel.

If a custom Persistent Object Model is used, then an Entity must implement the Channel interface before it can be used by the Chat Components framework.

To return all the members from a selected channel, the DBChannelWithMembers object is implemented.

Default channel entity

The DBChannel entity is defined with the following attributes:

Name	Type	Description
id	String	Unique identifier for the object. Used as a primary key.
type	String	Functional type of the channel. Common examples are common and group.
name	String	Name of the channel.
details	String?	Channel details that can be displayed alongside the name.
avatarURL	String?	Image that can be used to visually represent the channel.
custom	ChannelCustomData	Custom key value pairs that can be stored with the channel.
updated	String?	Last time the remote object was changed.
eTag	String?	Caching value that changes whenever the remote object changes.

The ChannelCustomData typealias is a map which stores additional key-value properties.

typealias ChannelCustomData = HashMap<String, Any>

Custom channel entity

To create a custom Persistent Object Model, you must implement the Channel interface.

The following properties are required:

val id: ChannelId
val name: String
val description: String?
val updated: String?
val eTag: String?
val type: String
val avatarURL: String?
val custom: Any?

Relationships

The DBChannelWithMembers entity contains the following attributes:

Name	Type	Description
channel	DBChannel	Entity of the channel object.
members	List<DBMember>	List of members with membership in a selected channel.

Repository

PubNub Chat Components for Android use a default channel repository named DefaultChannelRepository.

If you want to use a custom Persistent Object Model, create a custom ViewModel in which your Repository implements the ChannelRepository interface before it can be used by the Chat Components framework.

Default channel repository

The DefaultChannelRepository implementation is defined with the following attributes:

Name	Type	Description
channelDao	ChannelDao<DBChannel, DBChannelWithMembers>	Room's data access object (DAO) for the channel entity.

The ChannelDao interface uses both DBChannel and DBChannelWithMembers types. The first one is used for CRUD operations (Create, Read, Update, Delete) and the second one defines the type of the returned object.

Custom channel repository

To create a custom channel repository, implement the ChannelRepository interface.

These are the required methods:

• get()

Used to get one Channel object with specified id from the database. It returns null, when the object doesn't exist.

suspend fun get(id: ChannelId): Data?

• getAll()

Returns the paginated source of channels.

fun getAll(
  id: UserId? = null,
  filter: Query? = null,
  vararg sorted: Sorted = emptyArray(),
): PagingSource<Int, Data>

Name	Type	Description
id	UserId?	If specified, this method returns only channels the user is a member of.
filter	Query?	Query filter for the database.
sorted	Sorted	Array of sorted keys and directions.

• getList()

Returns the list of all channels.

Example:

val repository: DefaultChannelRepository = LocalChannelRepository.current

val channels = remember {
  repository.getAll(
    id = "my-user-id",
    filter = Query("type LIKE ?", "group"),
    sorted = arrayOf(Sorted("type", Sorted.Direction.ASC)),
  )
}

suspend fun getList(): List<Data>

• add()

Adds a new channel object to the database.

suspend fun add(vararg channel: DB)

• remove()

Removes the channel object with the specified ID.

suspend fun remove(id: ChannelId)

• size()

Returns the number of all channels.

suspend fun size(): Long

Network data

The PNChannelMetadata class is used to communicate with PubNub APIs to send and receive channel metadata.

Name	Type	Description
id	String	Unique identifier for the object.
name	String	Name of the channel.
description	String?	Channel details that can be displayed alongside the name.
custom	Any	Custom key value pairs that can be stored with the channel.
updated	String?	Last time the remote object was changed.
eTag	String?	Caching value that changes whenever the remote object changes.

Custom channel data

PNChannelMetadata contains the custom property. You can use it to store a custom object. In the default implementation, NetworkChannelMapper is implemented to parse the custom object to ChannelCustomData.

Service

PubNub Chat Components for Android use a default service named DefaultChannelServiceImpl. This service is responsible for synchronizing PubNub APIs network channel data and storing it in the local database.

You can obtain the instance or override it using LocalChannelService in CompositionLocalProvider. If you want to use a custom service, you need to create a class which implements the ChannelService interface.

Default channel service

The DefaultChannelServiceImpl implementation is defined with the following attributes:

Name	Type	Description
pubNub	PubNub	PubNub instance.
channelRepository	ChannelRepository<DBChannel, DBChannelWithMembers>	The ChannelRepository implementation responsible for CRUD operations (Create, Read, Update, Delete) on channel objects in the database.
networkMapper	NetworkChannelMapper	Network object to database object mapper.
errorHandler	ErrorHandler	Instance of the error handling class.
coroutineScope	CoroutineScope	Scope for new coroutines.
dispatcher	CoroutineDispatcher	Coroutine dispatcher implementation.

Custom channel service

To create a custom channel service, implement the ChannelService interface and pass it as a parameter to the composition tree. You can do it by wrapping ChatProvider with CompositionLocalProvider.

CompositionLocalProvider(LocalChannelService provides MyChannelServiceImpl){
  ChatProvider(…)
}

These are the required methods:

• bind()

Subscribes to the channels and sets listeners for channel events.

fun bind(vararg channels: String)

• unbind()

Removes the listeners and unsubscribes from channels.

fun unbind()

• getAll()

Fetches all the channel metadata from the PubNub API and stores it in the local repository.

fun getAll(
  limit: Int? = null,
  page: PNPage? = null,
  filter: String? = null,
  sort: Collection<PNSortKey> = listOf(),
  includeCustom: Boolean = true,
)

• add()

Sets channel metadata in the PubNub API.

fun add(channel: DBChannel, includeCustom: Boolean)

• remove()

Removes channel metadata with a specified ID from the PubNub API.

fun remove(id: ChannelId)

Member

The users that are associated with a channel are also known as its members. A user might have many channel memberships and a channel might have multiple members.

Persistent data

The default Persistent Object Model inside the Chat Components defines an Entity named DBMember.

If a custom Persistent Object Model is used, then an Entity must implement the Member interface before it can be used by the Chat Components framework.

Default member entity

The DBMember entity is defined with the following attributes:

Name	Type	Description
id	UserId	A unique identifier for the object. Used as a Primary Key
name	String	Name of the user.
email	String?	Email address of the user.
externalId	String?	A unique external identifier for the user.
profileUrl	String?	Image that can be used to visually represent the user.
custom	CustomData	Custom object to store a description of the user.
updated	String?	Last time the remote object was changed.
eTag	String?	Caching value that changes whenever the remote object changes.

The CustomData data class stores an additional description of the user.

data class CustomData(
  val description: String
)

Custom member entity

To create a custom Persistent Object Model, you must implement the Member interface.

The following properties are required:

val id: UserId
val name: String
val email: String?
val externalId: String?
val profileURL: String?
val updated: String?
val eTag: String?
val custom: Any?

Relationships

The DBMemberWithChannels entity contains the following attributes:

Name	Type	Description
member	DBMember	Entity of a member object.
channels	List<DBChannel>	List of channels with membership.

Repository

PubNub Chat Components for Android use a default member repository named DefaultMemberRepository.

If a custom Persistent Object Model is used, then a Repository must implement the MemberRepository interface before it can be used by the Chat Components framework. Also, you must implement a custom view model.

Default member repository

The DefaultMemberRepository implementation is defined with the following attributes:

Name	Type	Description
memberDao	MemberDao<DBMember, DBMemberWithChannels>	Room DAO for the member entity.

The MemberDao interface uses both DBMember and DBMemberWithChannels types. The first one is used for CRUD operations (Create, Read, Update, Delete) and the second one defines the type of the returned object.

Custom member repository

To create a custom member repository, you must implement a MemberRepository interface.

The following methods are required:

• get()

Used to get one member object with specified id from the database. Returns null when the object doesn't exist.

suspend fun get(id: UserId): Data?

• getAll()

Returns paginated source of Members. Possible arguments are:

fun getAll(
  id: ChannelId? = null,
  filter: Query? = null,
  vararg sorted: Sorted = emptyArray(),
): PagingSource<Int, Data>

Name	Type	Description
id	ChannelId?	If specified, returns all members of the channel with the specified ID.
filter	Query?	Query filter for the database.
sorted	Sorted	Array of sorted keys and directions.

Example:

val repository: DefaultMemberRepository = LocalMemberRepository.current

val members = remember {
  repository.getAll(
    id = "channel-id",
    filter = Query("name LIKE ?", "Android"),
    sorted = arrayOf(Sorted("name", Sorted.Direction.ASC)),
  )
}

• getList()

If id is specified, it returns the list of members of the specified channel. Otherwise, it returns the list of all members.

suspend fun getList(id: ChannelId? = null): List<Data>

• add()

Adds a new member object to the database.

suspend fun add(vararg member: DB)

• remove()

Removes the member object with the specified ID.

suspend fun remove(id: UserId)

• size()

Returns the number of all members.

suspend fun size(): Long

Network data

The PNUUIDMetadata class is used to communicate with PubNub APIs to send and receive user metadata.

Name	Type	Description
id	String	Unique identifier for the object.
name	String?	Name of the user.
email	String?	Email address of the user.
externalId	String?	Unique external identifier for the user.
profileUrl	String?	Image that can be used to visually represent the user.
custom	Any?	Custom object to store extra data.
updated	String?	Last time the remote object was changed.
eTag	String?	Caching value that changes whenever the remote object changes.

Custom member data

The PNUUIDMetadata contains the custom property. You can use it to store a custom object. In the default implementation, NetworkMemberMapper is implemented to parse the custom object to CustomData.

Service

PubNub Chat Components for Android use a default service named DefaultMemberServiceImpl. This service is responsible for synchronizing PubNub APIs network member data and storing it in the local database.

You can obtain the instance or override it using LocalMemberService in CompositionLocalProvider. If you want to use a custom service, you need to create class which implements the MemberService interface.

Default member service

The DefaultMemberServiceImpl implementation is defined with the following attributes:

Name	Type	Description
pubNub	PubNub	PubNub instance.
memberRepository	MemberRepository<DBMember, DBMemberWithChannels>	The MemberRepository implementation responsible for CRUD operations (Create, Read, Update, Delete) on member objects in the database.
networkMapper	NetworkMemberMapper	Network object to database object mapper.
errorHandler	ErrorHandler	Instance of the error handling class.
coroutineScope	CoroutineScope	Scope for new coroutines.
dispatcher	CoroutineDispatcher	Coroutine dispatcher implementation.

Custom member service

To create a custom member service, implement the MemberService interface and pass it as a parameter to the composition tree. You can do it by wrapping ChatProvider with CompositionLocalProvider:

CompositionLocalProvider(LocalMemberService provides MyMemberServiceImpl){
  ChatProvider(…)
}

These are the required methods:

• bind()

Subscribes to the member channels and sets listeners for member metadata events.

fun bind(vararg channels: String)

• unbind()

Removes the listeners and unsubscribes from member channels.

fun unbind()

• getAll()

Fetches all the member metadata from the PubNub API and stores it in the local repository.

fun getAll(
  limit: Int? = null,
  page: PNPage? = null,
  filter: String? = null,
  sort: Collection<PNSortKey> = listOf(),
  includeCustom: Boolean = true,
)

• add()

Sets member metadata in the PubNub API.

fun add(member: DBMember, includeCustom: Boolean)

• remove()

Removes member metadata with a specified ID from the PubNub API.

fun remove(id: MemberId)

Message

A message is the dynamic content that a user sends to other users inside a channel.

Persistent data

The default Persistent Object Model inside the Chat Components defines an Entity named DBMessage.

If a custom Persistent Object Model is used, then an Entity must implement the Message interface before it can be used by the Chat Components framework.

Default message entity

The DBMessage entity is defined with the following attributes:

Name	Type	Description
id	String	Unique identifier for the object. Used as a primary key.
type	String	Functional type of the message. Common examples are default or reply. Refer to NetworkMessage.Type for more information.
text	String	Text of the message.
attachment	List<DBAttachment>?	List of attachments.
custom	Map<String, Any>?	Custom key value pairs that can be stored with the message.
publisher	UserId	ID of the message publisher.
channel	ChannelId	ID of the channel the message is published on.
timetoken	Timetoken	Time when a message was published.
isSent	Boolean	Information if a message was sent successfully.
exception	String?	Error details when an exception is thrown.

The DBAttachment is an abstract class which is a supertype for the Image, Link, and Custom classes:

@Keep
abstract class DBAttachment private constructor() : Attachment {
    @Keep
    data class Image(
        val imageUrl: String,
        override val type: String = "image",
        override val custom: Any? = null
    ) : DBAttachment()

    @Keep
    data class Link(
        val link: String,
        override val type: String = "link",
        override val custom: Any? = null
    ) : DBAttachment()

    @Keep
    data class Custom(
        override val type: String = "custom",
        override val custom: Any?
    ) : DBAttachment(
}

Custom message entity

To create a custom Persistent Object Model, you must implement the Message interface.

The following properties are required:

val id: MessageId
val type: String
val text: String?
val attachment: List<Attachment>?
val custom: Any?
val publisher: UserId
val channel: ChannelId
val timetoken: Timetoken
val isSent: Boolean
var exception: String?

Additionally, the Attachment interface has the following properties:

interface Attachment {
  val type: String
  val custom: Any?
}

Repository

PubNub Chat Components for Android use a default message repository named DefaultMessageRepository.

If you want to use a custom Persistent Object Model, a Repository must implement the MessageRepository interface before it can be used by the Chat Components framework. Also, you must implement a custom view model.

Default message repository

The DefaultMessageRepository implementation is defined with the following attributes:

Name	Type	Description
messageDao	MessageDao<DBMessage, DBMessage>	Room DAO for the message entity.

The MessageDao interface uses the DBMessage type for CRUD operations (Create, Read, Update, Delete) and to define the type of the returned object.

Custom message repository

To create a custom message repository, implement the MessageRepository interface.

The following methods are required:

• get()

Used to get one message object with a specified id from the database. Returns null when the object doesn't exist.

suspend fun get(id: MessageId): Data?

• getList()

Returns the list of all messages from a specified id.

suspend fun getList(
  id: ChannelId,
  count: Int,
  before: Boolean,
  timestamp: Long,
): List<Data>

These are the expected arguments:

Name	Type	Description
id	ChannelId	Specifies a channel to return messages from.
count	Int	Specifies the number of messages to return.
before	Boolean	Retrieves history messages before or after a specified timestamp.
timestamp	Long	Gets messages before or after a given time, based on the value in the before field.

• getAll()

Returns a paginated source of channels.

fun getAll(
  id: ChannelId? = null,
  filter: Query? = null,
  vararg sorted: Sorted = emptyArray(),
): PagingSource<Int, Data>

Possible arguments are:

Name	Type	Description
id	ChannelId?	If specified, it returns only messages from a specified ID.
filter	Query?	Query filter for the database.
sorted	Sorted	Array of sorted keys and directions.

Example:

val repository: DefaultMessageRepository = LocalMessageRepository.current

val messages = remember {
  repository.getAll(
    id = "my-channel-id",
    filter = Query("publisher LIKE ?", "my-uuid"),
    sorted = arrayOf(Sorted("type", Sorted.Direction.ASC)),
  )
}

• getLast()

Returns the last message from a given channel.

suspend fun getLast(channelId: String): Data?

• getLastByChannel()

Returns a flowable list of most recent messages (in a specified number) from a given channel.

fun getLastByChannel(id: ChannelId, count: Long): Flow<List<Data>>

Name	Type	Description
id	String	Channels to return messages from a specified ID.
count	Long	Number of messages to return.

• hasMoreBefore()

Returns true when any message with older timestamp than specified exists in database for a given channel.

suspend fun hasMoreBefore(id: ChannelId, timestamp: Timetoken): Boolean

• hasMoreAfter()

Returns true when any message with a newer timestamp than specified exists in a database for a given channel.

suspend fun hasMoreAfter(id: ChannelId, timestamp: Timetoken): Boolean

• add()

Adds a new message object to the database.

suspend fun add(vararg message: DB)

• remove()

Removes a message object from the database.

suspend fun remove(message: DB)

• removeAll()

Removes all messages from a given channel.

suspend fun removeAll(id: ChannelId)

• update()

Updates a specified message in the database.

suspend fun update(message: DB)

• has()

Checks if there is a message with a specified ID.

suspend fun has(id: MessageId): Boolean

• setSent()

Sets the message sent status.

suspend fun setSent(
  id: MessageId,
  timestamp: Timetoken? = null,
)

• setSendingError()

Sets the message error status.

suspend fun setSendingError(
  id: MessageId,
  exception: String? = null,
  timestamp: Timetoken? = null,
)

• getLastTimestamp()

Returns the last known timestamp of the message in the channel.

suspend fun getLastTimestamp(id: ChannelId): Long

Network data

The PNMessageResult class is used to communicate with PubNub APIs. The message field is mapped to the NetworkMessage class:

Name	Type	Description
id	String	Unique identifier for the object.
type	String	Type of the message: "default", "reply", "ephemeral", "error", "system", "custom".
text	String?	Content of the message.
attachment	List<Attachment>?	List of attachments.
custom	Any?	Custom key value pairs that can be stored with the channel.

Custom message data

The NetworkMessage contains custom property. This one might be used to store custom object. In default implementation, the NetworkMessageMapper and NetworkMessageHistoryMapper are used to map it.

Service

PubNub Chat Components for Android use a default service named DefaultMessageServiceImpl. This service is responsible for synchronizing PubNub APIs network message data and storing it in the local database.

You can obtain the instance or override it using LocalMessageService in CompositionLocalProvider. If you want to use a custom service, you need to create a class which implements the MessageService interface.

Default message service

The DefaultMessageServiceImpl implementation is defined with the following attributes:

Name	Type	Description
pubNub	PubNub	PubNub instance.
messageRepository	essageRepository<DBMessage, DBMessage>	The MessageRepository implementation responsible for CRUD operations (Create, Read, Update, Delete) on message objects in the database.
networkMapper	NetworkMessageMapper	Network object to database object mapper.
networkHistoryMapper	NetworkMessageHistoryMapper	Network history object to database object mapper.
errorHandler	ErrorHandler	Instance of the error handling class.
coroutineScope	CoroutineScope	Scope for new coroutines.
dispatcher	CoroutineDispatcher	Coroutine dispatcher implementation.

Custom message service

To create a custom member service, implement the MessageService interface and pass it as a parameter to the composition tree. You can do it by wrapping ChatProvider with CompositionLocalProvider:

CompositionLocalProvider(LocalMessageService provides MyMessageServiceImpl){
  ChatProvider(…)
}

These are the required methods:

• bind()

Sets listeners for message events.

fun bind()

• unbind()

Removes the listeners.

fun unbind()

• send()

Sends a message to a selected channel.

suspend fun send(
  id: ChannelId,
  message: Data,
  meta: Any? = null,
  store: Boolean = true,
  onSuccess: (String, Timetoken) -> Unit = { message, result -> Timber.i("Message '$message' sent, result: $result") },
  onError: (Exception) -> Unit = { Timber.i("Message sending error: $it") },
)

These are the expected arguments:

Name	Type	Description
id	ChannelId	Specifies a channel to send a message to.
message	Data	Message data object to send.
meta	Any?	Additional metadata to send.
store	Boolean	The flag denoting to store a message in history.
onSuccess	(String, Timetoken) -> Unit	Callback to invoke when a message is sent successfully.
onError	(Exception) -> Unit	Callback to invoke when there is an error while sending a message.

• pullHistory()

Pulls the messages from the PubNub History API.

suspend fun pullHistory(
  id: ChannelId,
  start: Long?,
  end: Long?,
  count: Int,
  withActions: Boolean = false,
  withUUID: Boolean = false
)

These are the expected arguments:

Name	Type	Description
id	ChannelId	Specifies a channel to return history messages from.
start	Long?	Delimits the start of a time slice (exclusive) to pull messages from.
end	Long?	Delimits the end of a time slice (inclusive) to pull messages from.
count	Int	Specifies the number of historical messages to return.
withActions	Boolean	Retrieves history messages with message actions.
withUUID	Boolean	Includes a publisher UUID with every history message.