The driving force behind MessageKit is the MessageType protocol which provides the minimum requirements for your own native message model. The MessageType protocol has the following 4 required properties:

public protocol MessageType {

    var sender: SenderType { get }

    var messageId: String { get }

    var sentDate: Date { get }

    var kind: MessageKind { get }
}

First, each MessageType is required to have a SenderType which contains two properties, senderId and displayName:

public protocol SenderType {

    var senderId: String { get }
    
    var displayName: String { get }
}

MessageKit uses the SenderType type to determine if a message was sent by the current user or to the current user.

Second, each message must have its own messageId which is a unique String identifier for the message.

Third, each message must have a sentDate which represents the Date that each message was sent.

Fourth, each message must specify what kind of message it is through the kind: MessageKind property:

MessageKind has 8 different cases representing the types of messages that MessageKit can display.

• text(String) - Use this case if you just want to display a normal text message without any attributes.

  • NOTE: You must also specify the UIFont you want to use for this text by setting the messageLabelFont property of the textMessageSizeCalculator in MessagesCollectionViewFlowLayout.

• attributedText(NSAttributedString) - Use this case if you want to display a text message with attributes.

  • NOTE: It is recommended that you use attributedText for text messages.

• emoji(String) - Use this case to display a message that only contains emoji.

  • NOTE: You must also specify the UIFont you want to use for this text by setting the messageLabelFont property of the emojiMessageSizeCalculator in MessagesCollectionViewFlowLayout.

• photo(MediaItem) - Use this case to display a photo message.

• video(MediaItem) - Use this case to display a video message.

• location(LocationItem) - Use this case to display a location message.

• audio(AudioItem) - Use this case to display an audio message.

• contact(ContactItem) - Use this case to display a contact message.

To begin using MessageKit you first need to subclass MessagesViewController:

class ChatViewController: MessagesViewController {
	override func viewDidLoad() {
		super.viewDidLoad()
	}
}

NOTE: If you override any of the UIViewController lifecycle methods such as viewDidLoad, viewWillAppear, viewDidAppear, make sure to call the superclass implementation of these methods.

In order to start displaying messages in your MessagesViewController subclass, you NEED to conform to the following 3 protocols:

1. MessagesDataSource
2. MessagesLayoutDelegate
3. MessagesDisplayDelegate

class ChatViewController: MessagesViewController {
	override func viewDidLoad() {
		super.viewDidLoad()
		messagesCollectionView.messagesDataSource = self
		messagesCollectionView.messagesLayoutDelegate = self
		messagesCollectionView.messagesDisplayDelegate = self
	}
}

You must implement the following 3 methods to conform to MessagesDataSource:

public struct Sender: SenderType {
    public let senderId: String

    public let displayName: String
}

// Some global variables for the sake of the example. Using globals is not recommended!
let sender = Sender(senderId: "any_unique_id", displayName: "Steven")
let messages: [MessageType] = []

extension ChatViewController: MessagesDataSource {

	var currentSender: SenderType {
		return Sender(senderId: "any_unique_id", displayName: "Steven")
	}

	func numberOfSections(in messagesCollectionView: MessagesCollectionView) -> Int {
		return messages.count
	}

	func messageForItem(at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageType {
		return messages[indexPath.section]
	}
}

NOTE: If you look closely at the implementation of the messageForItem method you'll see that we use the indexPath.section to retrieve our MessageType from the array as opposed to the traditional indexPath.row property. This is because the default behavior of MessageKit is to put each MessageType is in its own section of the MessagesCollectionView.

If you want to override this behavior, you can specify the number of items in each section through the numberOfItems method of MessagesDataSource.

As you can see MessageKit does not require you to return a MessagesCollectionViewCell like the traditional UITableView or UICollectionView API. All that is required is for you to return your MessageType model object. We take care of applying the model to the cell for you.

The MessagesLayoutDelegate and MessagesDisplayDelegate don't require you to implement any methods as they have default implementations for everything. You just need to make your MessagesViewController subclass conform to these two protocols and set them in the MessagesCollectionView object.

extension ChatViewController: MessagesDisplayDelegate, MessagesLayoutDelegate {}