Chatto

Chatto is a Swift lightweight framework to build chat applications. It's been designed to be extensible and performant. Along with Chatto there is ChattoAdditions, a companion framework which includes cells for messages and an extensible input component. You can find more details about how it was implemented in our blog. See them in action!

Features

• Calculation of collection view changes and layout in background
• Supports pagination in both directions and autoloading
• Message count contention for fast pagination and rotation with thousands of messsages
• Accessory view revealing by swiping from right
• Interactive keyboard dismissal
• Text bubbles
• Photo bubbles
• Extensible input bar

How to use

1. Subclass BaseChatViewController
2. Override createChatInputView() to use ChattoAdditions.ChatInputBar or provide your own component
3. Provide a data source with your messages
4. Override createPresenterBuilders(). There will be a presenter for each message that will be responsible for the UI of that message.

override func createPresenterBuilders() -> [ChatItemType: [ChatItemPresenterBuilderProtocol]] {
    return [
        TextMessageModel.chatItemType: [
            TextMessagePresenterBuilder(
                viewModelBuilder: TextMessageViewModelDefaultBuilder<TextMessageModel>(),
                interactionHandler: TextMessageHandler(baseHandler: self.baseMessageHandler)
            )
        ]
    ]
}

override func createChatInputView() -> UIView {
    let chatInputView = ChatInputBar.loadNib()
    self.configureChatInputBar(chatInputView)
    self.chatInputPresenter = ChatInputBarPresenter(chatInputView: chatInputView, chatInputItems: self.createChatInputItems())
    return chatInputView
}

override func viewDidLoad() {
    super.viewDidLoad()
    self.chatDataSource = self.myDataSource
}

Data source

The only requirement for your data source items is to conform to the ChatItemProtocol protocol, which basically asks for a unique identifier (uid) and a type. The uid will be used to calculate changes in the collection view and the type to quickly find a presenter builder for it. Your data source must conform to ChatDataSourceProtocol:

public protocol ChatDataSourceProtocol: class {
    var hasMoreNext: Bool { get }
    var hasMorePrevious: Bool { get }
    var chatItems: [ChatItemProtocol] { get }
    weak var delegate: ChatDataSourceDelegateProtocol? { get set }

    func loadNext(completion: () -> Void)
    func loadPrevious(completion: () -> Void)
    func adjustNumberOfMessages(preferredMaxCount preferredMaxCount: Int?, focusPosition: Double, completion:(didAdjust: Bool) -> Void) // If you want, implement message count contention for performance, otherwise just call completion(false)
}

If you want to handle smooth loading of new pages, or more challenging, smooth rotation with thousands of messages (calculating 10K text message sizes can take ~15s on iPhone 4s) you should opt-in for adjustNumberOfMessages(preferredMaxCount:focusPosition:completion:). See how it's done in ChattoApp!

Presenters

The presenter is the key entity that enables scalability in Chatto's architecture. Each message will be paired with a presenter who will be responsible for the UI related to that message (cell configuration, calculation of size, user handling,... ). Take a look at TextMessagePresenter, PhotoMessagePresenter in ChattoAdditions and ChatItemPresenterProtocol

public protocol ChatItemPresenterProtocol: class {
    static func registerCells(collectionView: UICollectionView)
    var canCalculateHeightInBackground: Bool { get } // Default is false
    func heightForCell(maximumWidth width: CGFloat, decorationAttributes: ChatItemDecorationAttributesProtocol?) -> CGFloat
    func dequeueCell(collectionView collectionView: UICollectionView, indexPath: NSIndexPath) -> UICollectionViewCell
    func configureCell(cell: UICollectionViewCell, decorationAttributes: ChatItemDecorationAttributesProtocol?)
    func cellWillBeShown(cell: UICollectionViewCell) // optional
    func cellWasHidden(cell: UICollectionViewCell) // optional
    func shouldShowMenu() -> Bool // optional. Default is false
    func canPerformMenuControllerAction(action: Selector) -> Bool // optional. Default is false
    func performMenuControllerAction(action: Selector) // optional
}

Decoration

As you may have noticed, there's an interesting decorationAttributes parameter in configureCell(_:decorationAttributes:)

public protocol ChatItemDecorationAttributesProtocol {
    var bottomMargin: CGFloat { get }
}

Decoration attributes have two different purposes:

1. Provide margins for ChatCollectionViewLayout
2. Provide context to your presenters so you can further customize your UI (for instance to flag if a bubble should show the tail)

By default, no decorationAttributes will be provided to your presenters, and the margin between messages will be zero. You may opt-in for a message decorator as in ChattoApp

public protocol ChatItemsDecoratorProtocol {
    func decorateItems(chatItems: [ChatItemProtocol]) -> [DecoratedChatItem]
}

In your decorator you may even create new ChatItems. The decorator in ChattoApp not only provides different margins for the bubbles, but it also inserts new ChatItems that represents sending/failed status. Decoration happens in background so the UI stays responsive while scrolling.

Input bar

You can return your own input component when overriding createChatInputView() or use ChattoAdditions.ChatInputBar

ChattoAdditions.ChatInputBar is an extensible component on its own. Each input item defines a tabView that serves as the call to action to activate that input item and an inputView with your custom input UI. ChatInputBarPresenter will take a collection of ChatInputItemProtocol and it will configure ChatInputBar to display them.

public protocol ChatInputItemProtocol: AnyObject {
    var tabView: UIView { get }
    var inputView: UIView? { get }
    var presentationMode: ChatInputItemPresentationMode { get }
    var showsSendButton: Bool { get }
    var selected: Bool { get set }

    func handleInput(input: AnyObject)
}

How to install

CocoaPods

1. Make sure use_frameworks! is added to your Podfile.

2. Include the following in your Podfile:

   pod 'Chatto', '= 1.0.0'
   pod 'ChattoAdditions', '= 1.0.0' # if you want to use the cells or the input component
   

If you like to live on the bleeding edge, you can use the master branch with: pod 'Chatto', :git => 'https://github.com/badoo/Chatto' pod 'ChattoAdditions', :git => 'https://github.com/badoo/Chatto' 3. Run pod install

Carthage

If you’re using Carthage, simply add Chatto to your Cartfile:

github "badoo/Chatto"

Manually

1. Clone, add as a submodule or download.
2. Drag and drop Chatto and/or ChattoAdditions project to your workspace
3. Add Chatto and/or ChattoAdditions to Embedded binaries

License

Source code is distributed under MIT license.

##Blog Read more on our tech blog or explore our other open source projects