Updated README.md with updateData documentation

README.md

@@ -83,23 +83,47 @@ However, if we decided to sort it so that deletions and higher indices are proce
 
 ### Table and Collection Views
 
-```swift
-// The following will automatically animate deletions, insertions, and moves:
 
-tableView.animateRowChanges(oldData: old, newData: new)
+The following will automatically animate deletions, insertions, and moves:
 
-collectionView.animateItemChanges(oldData: old, newData: new)
+```swift
+tableView.animateRowChanges(oldData: old, newData: new)
 
-// It can work with sections, too!
+collectionView.animateItemChanges(oldData: old, newData: new, updateData: { self.dataSource = new })
+```
 
+It can work with sections, too!
+```swift
 tableView.animateRowAndSectionChanges(oldData: old, newData: new)
 
-collectionView.animateItemAndSectionChanges(oldData: old, newData: new)
+collectionView.animateItemAndSectionChanges(oldData: old, newData: new, updateData: { self.dataSource = new })
+```
 
+You can also calculate `diff` separately and use it later:
+```swift
+// Generate the difference first
+let diff = dataSource.diff(newDataSource)
+
+// This will apply changes to dataSource.
+let dataSourceUpdate = { self.dataSource = newDataSource }
+
+// ...
+
+tableView.apply(diff)
+
+collectionView.apply(diff, updateData: dataSourceUpdate)
 ```
 
 Please see the [included examples](/Examples/) for a working sample.
 
+#### Note about `updateData`
+
+Since version `2.0.0` there is now an `updateData` closure which notifies you when it's an appropriate time to update  `dataSource` of your `UICollectionView`. This addition refers to UICollectionView's [performbatchUpdates](https://developer.apple.com/documentation/uikit/uicollectionview/1618045-performbatchupdates):
+
+> If the collection view's layout is not up to date before you call this method, a reload may occur. To avoid problems, you should update your data model inside the updates block or ensure the layout is updated before you call `performBatchUpdates(_:completion:)`.
+
+Thus, it is **recommended** to update your `dataSource` inside `updateData` closure to avoid potential crashes during animations.
+
 ### Using Patch and Diff
 
 When you want to determine the steps to transform one collection into another (e.g. you want to animate your user interface according to changes in your model), you could do the following: