iOS Chat Component 
- Description
- Installation
- Architecture
- Writing custom UI layer
- Writing custom networking layer
- Gluing UI layer and networking layer
- Usage
Description
This repository contains an universal chat framework that can be easily scaled to be used in any project that contains standard in-app chat component. This library is divided into multiple modules (layers). Each module is a standalone framework target, so the implementation details can be hidden from each other. Each module is its own pod as well.
Installation
CocoaPods
To integrate Chat Component into your Xcode project using CocoaPods, specify it in your Podfile:
source 'https://cdn.cocoapods.org/'
target 'TARGET_NAME' do
# For plug&play solution with predefined MessageKit UI and Firestore backend
pod 'STRVChat'
# If you want to use just some of the layers
pod 'STRVChat/Core'
pod 'STRVChat/NetworkingFirestore'
pod 'STRVChat/UI'
end
Initialization
Default chat component implementation uses background fetches and scheduled task and has to be instantiated in app's delegate didFinishLaunchingWithOptions method.
Example
See the sample app for an example how to use this pod.
Architecture
The library consists of four modules:
- Chat
- ChatCore
- ChatNetworkingFirestore
- ChatUI
See this diagram for a visual overview of the architecture:
ChatCore - Essential models and protocols
ChatCore
The main class that the UI can use for all chat operations. It contains all the necessary methods and implements ChatCoreServicing protocol.
DataPayload
This class carries the data received from a listener (for example collection of conversations) plus the information whether end of the data has been reached. This is useful for the UI to be able to hide "Load more" button for example. It could possibly contain some more meta data in the future.
ChatNetworkingFirestore - Firestore networking layer (optional)
You can use this pod if your project uses Firestore as the database for the chat. If you need to use another API, you can write your own networking layer. See Writing custom networking layer
ChatUI - UI using MessageKit (optional)
Simple UI implementation for testing. Most projects will probably want to write their own UI. See Writing custom UI layer.
Chat – Glue
You can use this part of the library in case you want to use existing implementations of ChatCoreServicing, ChatNetworkServicing and ChatUIServicing and you don't need anything custom. It contains the glue code necessary for all of the parts to work. Right now it contains only a chat solution for Pumpkin Pie project, but if you want to consruct your chat from different components, it's very simple. See Gluing UI layer and networking layer
Writing custom UI layer
The provided UI layer is fairly simple and doesn't offer any customization so usually in a project you will want to create your own UI layer. The only thing that is required is providing the ChatCore class with a ChatUIModels implementation that specifies which models should be provided to your completion handlers.
class ChatCore<Networking: ChatNetworkServicing, Models: ChatUIModels>: ChatCoreServicingpublic protocol ChatUIModels {
associatedtype CUI: ConversationRepresenting
associatedtype MUI: MessageRepresenting
associatedtype MSUI: MessageSpecifying
associatedtype USRUI: UserRepresenting
}Writing custom networking layer
The only thing needed to implement custom networking layer is conforming to the protocol ChatNetworkServicing and providing this implementation to ChatCore as seen in the next chapter.
Gluing UI layer and networking layer
Let's take the complete Pumpkin Pie solution mentioned above as an example.
First, you need your implementations of ChatNetworkServicing, ChatCoreServicing and ChatUIServicing. From now on, let's assume you want to use ChatCore as the implementation of ChatCoreServicing because it is written generically enough to work with any tuple of implementations of ChatNetworkServicing and ChatUIServicing. In case of Pumpkin Pie, those implementations are ChatNetworkFirestore and ChatUI.
Second, you need to make all your networking models conform to ChatUIConvertible, for example:
extension ConversationFirestore: ChatUIConvertible {
public var uiModel: Conversation {
// return Conversation instance created using data from `self`
}
public init(uiModel: Conversation) {
// call self.init using data from `uiModel`
}
}and make all your UI models conform to ChatNetworkingConvertible like this:
extension Conversation: ChatNetworkingConvertible {
public typealias NetworkingModel = ConversationFirestore
}Third, you need to make your implementation of ChatUIServicing compatible with ChatCore simply like this:
public class ChatUI<Core: ChatUICoreServicing>: ChatUIServicing {
...
}
public protocol ChatUICoreServicing: ChatCoreServicing where C == Conversation, M == MessageKitType, MS == MessageSpecification, U == User { }
extension ChatCore: ChatUICoreServicing where Models.CUI == Conversation, Models.MSUI == MessageSpecification, Models.MUI == MessageKitType, Models.USRUI == User { }Next, you need to wrap your implementation of ChatUIServicingin ChatInterfacing to manage different instances of UI for different scenes:
public class PumpkinPieInterface: ChatInterfacing {
public let identifier: ObjectIdentifier
public let uiService: ChatUI<...>
public weak var delegate: Delegate?
public var rootViewController: UIViewController {
uiService.rootViewController
}
init(...) {...}
}Finally, you glue everything together by implementing ChatSpecifying protocol:
public class PumpkinPieChat: DefaultChatSpecifying {
public typealias UIModels = ChatModelsUI
public typealias Networking = ChatNetworkingFirestore
public typealias Core = ChatCore<ChatNetworkingFirestore, UIModels>
public typealias Interface = PumpkinPieInterface
public init(...) {...}
func interface(with identifier: ObjectIdentifier) -> Interface {...}
func runBackgroundTasks(completion: @escaping (UIBackgroundFetchResult) -> Void) {...}
func resendUnsentMessages() {...}
func setCurrentUser(userId: EntityIdentifier, name: String, imageUrl: URL?) {...}
}Chat core usage
Listeners
Because chat is a real-time functionality, the client needs to be notified about any new data updates ASAP. That's why fetching conversations and messages is done using a persistent connection. Every time you call core.listenToConversations or core.listenToMessages you receive a ChatListener (just a String typealias for now) instance that you must store somewhere. Whenever you are ready to stop listening to this particular set of data, call core.remove(listener: ChatListener) so there is no unnecessary network connection left behind.
Send a message
core.send(message: .text(message: "Hello!"), to: currentChatId) { result in
// Called after successfuly sending a message
switch result {
case .success(let message):
print(message.id)
case .failure(let error):
print(error)
}
}Listen to conversations
core.listenToConversations { result in
// Called on every conversations update
switch result {
case .success(let payload):
// payload contains current list of fetched conversations
// as well as some additional data (see `DataPayload` for more info)
case .failure(let error):
print(error)
}
}Listen to messages of a conversation
core.listenToMessages(conversation: conversationId) { result in
// Called on every messages update
switch result {
case .success(let payload):
// payload contains current list of fetched conversations
// as well as some additional data (see `DataPayload` for more info)
case .failure(let error):
print(error)
}
}Pagination
Whenever you need to load next page of conversations or messages, simply call core.loadMoreConversations or core.loadMoreMessages respectively. The existing callbacks that you provided when calling core.listenTo... method will be called with updated set of data. (So on the first call to core.listenToConversations you will receive 1 * n number of conversations and after calling core.loadMoreConversations you will receive 2 * n number of conversations).
Task management
To make the chat core component well thought out it was enhanced by task manager. The task manager class allows chat core to make calls with extra attributes and handles all logic behind. Using task management impacts on completion handling at chat core itself.
Available attributes
- after init
- background task
- background thread
- retry (with retry type finite/infinite)
After init
Few calls (e.g. load conversations) can get into the task manager's queue, although chat core is not connected yet. Those tasks remain in the queue and, after the core is loaded, are executed.
Background task
Calls attributed background task will try to continue after app goes to the background. At first all tasks are hooked to app's beginBackgroundTaskWithName:expirationHandler: method. Secondary if iOS version is 13+ and there are still unfinished tasks in queue, then BGSCheduledTask is used to activate the app after some time to retry execution of those tasks. If the chat runs on an older version of iOS then background fetch is used.
Background thread
Tasks attributed background thread are run in its own dedicated background thread.
Retry
To allow tasks retry there are two options how to do it. Finite with limited amount of attempts and infinite. The infinite type is used for initial loading of the whole chat core. The finite retry type with the default value of attempts equal to 3 is used for sending messages. Please note that only the network error comes in place when handling retry, other errors don't count.
Example of call
You can find an example of the send message task method below. The task manager wraps send message network call and applies few attributes on it. In case of using retry attribute, it is necessary to control the response of taskCompletion closure, as it is shown in case of failure in the example.
taskManager.run(attributes: [.backgroundTask, .afterInit, .backgroundThread, .retry(.finite())]) { [weak self] taskCompletion in
let mess = Networking.MS(uiModel: message)
self?.networking.send(message: mess, to: conversation) { result in
switch result {
case .success(let message):
_ = taskCompletion(.success)
completion(.success(message.uiModel))
case .failure(let error):
if taskCompletion(.failure(error)) == .finished {
completion(.failure(error))
}
}
}
}Chat core states
When chat core is created there are few states which can change during its lifetime. It's possible to observe those changes so UI can react properly. Core contains reachability observer to check network connection availability.
Available states
- initial after core is created
- loading after init when core tries to connect to service provider and setup all stuff
- connected all loading work is done and core is ready to make its job
- connecting when core is notified that network went off
Caching unsent messages
When core sends message, it's automatically stored to local secure cache (keychain). After message is sent (eg. background task) its removed from cache. When sending fails for any reason, user has chance to retry or delete message at UI.
Features
Conversation
- List of conversations
- Get notified when conversations are updated
- Implement background fetch for retry mechanism
- Online status indicator
Message
- Get notified when create/update messages
- Read receipts - show a flag with a time and date next to a last message the other user read
- Cache messages that failed to be sent
- Retry mechanism for sending messages
- Continue with sending a message even if user sends an app to background
- Delete a message
User
- Name
- Avatar
Supported Message Types
- Text
- Photo
- Video
- Location
Future features
These features will be added in later stages of development but the framework must be developed with bearing them in mind.
- Persistence
- Moderation
- Extensions - RxSwift, PromiseKit...etc
- Typing indicator
- Notifications