MessagesDataSource & MessagesLayoutDelegate methods for MessageType.custom handling.

Sources/Controllers/MessagesViewController.swift

@@ -206,7 +206,7 @@ UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
             cell.configure(with: message, at: indexPath, and: messagesCollectionView)
             return cell
         case .custom:
-            fatalError(MessageKitError.customDataUnresolvedCell)
+            return messagesDataSource.customCell(for: message, at: indexPath, in: messagesCollectionView)
         }
     }
 

Sources/Layout/MessagesCollectionViewFlowLayout.swift

@@ -151,7 +151,7 @@ open class MessagesCollectionViewFlowLayout: UICollectionViewFlowLayout {
         case .location:
             return locationMessageSizeCalculator
         case .custom:
-            fatalError("Must return a CellSizeCalculator for MessageKind.custom(Any?)")
+            return messagesLayoutDelegate.cellSizeCalculator(for: message, at: indexPath, in: messagesCollectionView)
         }
     }
 

Sources/Protocols/MessagesDataSource.swift

@@ -92,6 +92,18 @@ public protocol MessagesDataSource: AnyObject {
     ///
     /// The default value returned by this method is `nil`.
     func messageBottomLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString?
+    
+    
+    /// Custom collectionView cell for message with `custom` message type.
+    ///
+    /// - Parameters:
+    ///   - message: The `custom` message type
+    ///   - indexPath: The `IndexPath` of the cell.
+    ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
+    ///
+    /// - Note:
+    ///   This method will call fatalError() on default. You must override this method if you are using MessageType.custom messages.
+    func customCell(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> UICollectionViewCell
 }
 
 public extension MessagesDataSource {
@@ -115,4 +127,8 @@ public extension MessagesDataSource {
     func messageBottomLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString? {
         return nil
     }
+    
+    func customCell(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> UICollectionViewCell {
+        fatalError(MessageKitError.customDataUnresolvedCell)
+    }
 }

Sources/Protocols/MessagesLayoutDelegate.swift

@@ -80,6 +80,18 @@ public protocol MessagesLayoutDelegate: AnyObject {
     /// - Note:
     ///   The default value returned by this method is zero.
     func messageBottomLabelHeight(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CGFloat
+    
+    
+    /// Cell size calculator for messages with MessageType.custom.
+    ///
+    /// - Parameters:
+    ///   - message: The custom message
+    ///   - indexPath: The `IndexPath` of the cell.
+    ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
+    ///
+    /// - Note:
+    ///   The default implementation will throw fatalError(). You must override this method if you are using messages with MessageType.custom.
+    func cellSizeCalculator(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CellSizeCalculator
 }
 
 public extension MessagesLayoutDelegate {
@@ -103,4 +115,8 @@ public extension MessagesLayoutDelegate {
     func messageBottomLabelHeight(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CGFloat {
         return 0
     }
+    
+    func cellSizeCalculator(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CellSizeCalculator {
+        fatalError("Must return a CellSizeCalculator for MessageKind.custom(Any?)")
+    }
 }