⚡ Bolt: Optimize @Published array mutations to reduce UI churn

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2024-05-20 - Batching @Published Array Mutations
+**Learning:** In SwiftUI ObservableObject view models, mutating individual elements of a @Published array property inside a loop triggers a UI update notification for every change.
+**Action:** Use functional methods like `map` to batch updates into a single property assignment, significantly reducing unnecessary UI recalculations. Always add comments explaining this optimization.

Sources/Cacheout/ViewModels/CacheoutViewModel.swift

@@ -172,14 +172,22 @@ class CacheoutViewModel: ObservableObject {
     }
 
     func selectAllSafe() {
-        for i in scanResults.indices where scanResults[i].category.riskLevel == .safe && !scanResults[i].isEmpty {
-            scanResults[i].isSelected = true
+        // Optimization: Batch @Published array update to prevent O(N) UI re-renders
+        scanResults = scanResults.map { result in
+            var copy = result
+            if copy.category.riskLevel == .safe && !copy.isEmpty {
+                copy.isSelected = true
+            }
+            return copy
         }
     }
 
     func deselectAll() {
-        for i in scanResults.indices {
-            scanResults[i].isSelected = false
+        // Optimization: Batch @Published array update to prevent O(N) UI re-renders
+        scanResults = scanResults.map { result in
+            var copy = result
+            copy.isSelected = false
+            return copy
         }
         deselectAllNodeModules()
     }
@@ -193,17 +201,32 @@ class CacheoutViewModel: ObservableObject {
     }
 
     func selectStaleNodeModules() {
-        for i in nodeModulesItems.indices where nodeModulesItems[i].isStale {
-            nodeModulesItems[i].isSelected = true
+        // Optimization: Batch @Published array update to prevent O(N) UI re-renders
+        nodeModulesItems = nodeModulesItems.map { item in
+            var copy = item
+            if copy.isStale {
+                copy.isSelected = true
+            }
+            return copy
         }
     }
 
     func selectAllNodeModules() {
-        for i in nodeModulesItems.indices { nodeModulesItems[i].isSelected = true }
+        // Optimization: Batch @Published array update to prevent O(N) UI re-renders
+        nodeModulesItems = nodeModulesItems.map { item in
+            var copy = item
+            copy.isSelected = true
+            return copy
+        }
     }
 
     func deselectAllNodeModules() {
-        for i in nodeModulesItems.indices { nodeModulesItems[i].isSelected = false }
+        // Optimization: Batch @Published array update to prevent O(N) UI re-renders
+        nodeModulesItems = nodeModulesItems.map { item in
+            var copy = item
+            copy.isSelected = false
+            return copy
+        }
     }
 
     /// Menu bar label: show free GB in the tray