Merge pull request #14 from scribd/stephane/delta_safety_check

DRY up safety check, move delegate call onto main thread.

Author: Stephane Magne

Sources/LiveCollections/Classes/Internal/ItemDataCalculator.swift

@@ -205,13 +205,7 @@ private extension ItemDataCalculator {
             self?._performNextCalculation()
         }
 
-        let isDeltaAccurate: Bool = (itemProvider.items.count + delta.insertions.count - delta.deletions.count) == updatedItems.count
-
-        if isDeltaAccurate == false {
-            calculationDelegate?.inaccurateDeltaDetected(delta)
-        }
-
-        guard delta.hasChanges, isDeltaAccurate else {
+        guard delta.hasChanges else {
             updateData()
             calculationCompletion()
             return
@@ -228,8 +222,13 @@ private extension ItemDataCalculator {
                 targetView.reloadData()
             }
 
+            let isDeltaInaccurate: Bool = (itemProvider.items.count + delta.insertions.count - delta.deletions.count) != updatedItems.count
+            if isDeltaInaccurate {
+                self.calculationDelegate?.inaccurateDeltaDetected(delta)
+            }
+
             let itemAnimationStlye: AnimationStyle = {
-                if targetView.frame.isEmpty { return .reloadData }
+                if targetView.frame.isEmpty || isDeltaInaccurate { return .reloadData }
                 guard let animationDelegate = animationDelegate else { return .preciseAnimations }
                 return animationDelegate.preferredItemAnimationStyle(for: delta)
             }()

Sources/LiveCollections/Classes/Internal/SectionDataCalculator.swift

@@ -277,13 +277,8 @@ private extension SectionDataCalculator {
 
             let currentItemCount: Int = sectionProvider.sections.reduce(0) { $0 + $1.items.count }
             let updatedItemCount: Int = updatedSections.reduce(0) { $0 + $1.items.count }
-            let isDeltaAccurate: Bool = (currentItemCount + itemDelta.insertions.count - itemDelta.deletions.count) == updatedItemCount
 
-            if isDeltaAccurate == false {
-                self.calculationDelegate?.inaccurateDeltaDetected(itemDelta)
-            }
-
-            guard (sectionDelta.hasChanges || itemDelta.hasChanges), isDeltaAccurate else {
+            guard sectionDelta.hasChanges || itemDelta.hasChanges else {
                 sectionProvider.calculatingSections = nil
                 calculationCompletion()
                 return // don't need to update with no changes
@@ -310,8 +305,13 @@ private extension SectionDataCalculator {
                     return
                 }
 
+                let isDeltaInaccurate: Bool = (currentItemCount + itemDelta.insertions.count - itemDelta.deletions.count) != updatedItemCount
+                if isDeltaInaccurate {
+                    self.calculationDelegate?.inaccurateDeltaDetected(itemDelta)
+                }
+
                 let itemAnimationStlye: AnimationStyle = {
-                    if view.frame.isEmpty { return .reloadData }
+                    if view.frame.isEmpty || isDeltaInaccurate { return .reloadData }
                     guard let animationDelegate = animationDelegate else { return .preciseAnimations }
                     return animationDelegate.preferredItemAnimationStyle(for: itemDelta)
                 }()