Adding support of mutable CellViewModels

Diff update: in case if moved items are equal, initial item is used for afterDeleteItems instead of final item. This allows to keep CellViewModel assigned to UICell.

Author: Mikhail Markin

CHANGELOG.md

@@ -5,6 +5,8 @@ All notable changes to this project will be documented in this file.
 
 #### Master
 
+* Added support of mutable CellViewModels.
+
 ## [4.0.1](https://github.com/RxSwiftCommunity/RxDataSources/releases/tag/4.0.1)
 
 * Fixes Carthage integration and reverts static frameworks to dynamic frameworks.

Sources/Differentiator/Diff.swift

@@ -623,8 +623,10 @@ public enum Diff {
                         let finalItem = finalItemCache[finalItemIndex.sectionIndex][finalItemIndex.itemIndex]
                         if finalItem != initialSections[i].items[j] {
                             updatedItems.append(ItemPath(sectionIndex: i, itemIndex: j))
+                            afterDeleteItems.append(finalItem)
+                        } else {
+                            afterDeleteItems.append(initialSections[i].items[j])
                         }
-                        afterDeleteItems.append(finalItem)
                     default:
                         try precondition(false, "Unhandled case")
                     }