⚡ Bolt: Batch @Published array updates in CacheoutViewModel

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2024-05-24 - Batching @Published Array Updates
+**Learning:** Mutating elements of a `@Published` array of structs in a `for` loop (e.g. `for i in array.indices { array[i].prop = val }`) inside an `ObservableObject` triggers a separate UI update for every single iteration, causing severe UI unresponsiveness and thrashing when dealing with many items (like `nodeModulesItems`).
+**Action:** Always use `.map` to create a new array and assign it back to the `@Published` property in a single operation, batching the UI updates.

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 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
+        scanResults = scanResults.map { result in
+            var copy = result
+            copy.isSelected = false
+            return copy
         }
         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 copy = item
+            if copy.isStale {
+                copy.isSelected = true
+            }
+            return copy
         }
     }
 
     func selectAllNodeModules() {
-        for i in nodeModulesItems.indices { nodeModulesItems[i].isSelected = true }
+        nodeModulesItems = nodeModulesItems.map { item in
+            var copy = item
+            copy.isSelected = true
+            return copy
+        }
     }
 
     func deselectAllNodeModules() {
-        for i in nodeModulesItems.indices { nodeModulesItems[i].isSelected = false }
+        nodeModulesItems = nodeModulesItems.map { item in
+            var copy = item
+            copy.isSelected = false
+            return copy
+        }
     }
 
     /// Menu bar label: show free GB in the tray