Potential fix for invalidation crashes

JosephDuffy · JosephDuffy · commit 8f0d651f5fc2 · 2020-11-03T13:09:45.000Z
As mentioned in #13 and #8 there are some scenarios where the collection view’s data is out-of-sync with the data in composed. As mentioned in #13 calling `layoutIfNeeded` can trigger the data to be in sync again. In this I have added it to `mappingWillBeginUpdating(_:)` which _appears_ to solve the problem. It might be needed in `replace(sectionProvider:)` (because `reloadData` is called) and/or `mappingDidInvalidate(_:)` (for the same reason) but I’m still investigating.
diff --git a/Sources/ComposedUI/CollectionView/CollectionCoordinator.swift b/Sources/ComposedUI/CollectionView/CollectionCoordinator.swift
@@ -217,6 +217,7 @@ extension CollectionCoordinator: SectionProviderMappingDelegate {
     public func mappingWillBeginUpdating(_ mapping: SectionProviderMapping) {
         reset()
         defersUpdate = true
+        collectionView.layoutIfNeeded()
     }
 
     public func mappingDidEndUpdating(_ mapping: SectionProviderMapping) {

Original file line number	Diff line number	Diff line change
`@@ -217,6 +217,7 @@ extension CollectionCoordinator: SectionProviderMappingDelegate {`
`217`	`217`	`public func mappingWillBeginUpdating(_ mapping: SectionProviderMapping) {`
`218`	`218`	`reset()`
`219`	`219`	`defersUpdate = true`
	`220`	`+ collectionView.layoutIfNeeded()`
`220`	`221`	`}`
`221`	`222`
`222`	`223`	`public func mappingDidEndUpdating(_ mapping: SectionProviderMapping) {`