⚡ Bolt: Batch @Published array updates to prevent UI stuttering

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2024-04-09 - Batch @Published array updates to prevent UI stuttering
+**Learning:** In SwiftUI `ObservableObject` view models, mutating individual elements of a `@Published` array property inside a loop triggers a UI update notification (`objectWillChange`) for every single change. For collections of value types (structs), this causes severe unnecessary UI recalculations and unresponsiveness during multi-select operations (like selecting 50+ node_modules directories).
+**Action:** Utilize functional methods like `map` to transform the entire collection and batch updates into a single property assignment. This significantly reduces unnecessary UI recalculations and improves responsiveness.

Sources/Cacheout/ViewModels/CacheoutViewModel.swift

@@ -172,14 +172,20 @@ class CacheoutViewModel: ObservableObject {
     }
 
     func selectAllSafe() {
-        for i in scanResults.indices where scanResults[i].category.riskLevel == .safe && !scanResults[i].isEmpty {
-            scanResults[i].isSelected = true
+        scanResults = scanResults.map { result in
+            var updated = result
+            if updated.category.riskLevel == .safe && !updated.isEmpty {
+                updated.isSelected = true
+            }
+            return updated
         }
     }
 
     func deselectAll() {
-        for i in scanResults.indices {
-            scanResults[i].isSelected = false
+        scanResults = scanResults.map { result in
+            var updated = result
+            updated.isSelected = false
+            return updated
         }
         deselectAllNodeModules()
     }
@@ -193,17 +199,29 @@ class CacheoutViewModel: ObservableObject {
     }
 
     func selectStaleNodeModules() {
-        for i in nodeModulesItems.indices where nodeModulesItems[i].isStale {
-            nodeModulesItems[i].isSelected = true
+        nodeModulesItems = nodeModulesItems.map { item in
+            var updated = item
+            if updated.isStale {
+                updated.isSelected = true
+            }
+            return updated
         }
     }
 
     func selectAllNodeModules() {
-        for i in nodeModulesItems.indices { nodeModulesItems[i].isSelected = true }
+        nodeModulesItems = nodeModulesItems.map { item in
+            var updated = item
+            updated.isSelected = true
+            return updated
+        }
     }
 
     func deselectAllNodeModules() {
-        for i in nodeModulesItems.indices { nodeModulesItems[i].isSelected = false }
+        nodeModulesItems = nodeModulesItems.map { item in
+            var updated = item
+            updated.isSelected = false
+            return updated
+        }
     }
 
     /// Menu bar label: show free GB in the tray