⚡ Optimize map annotation lookup from O(N) to O(1)

benchmark.swift

@@ -0,0 +1,38 @@
+import Foundation
+
+struct FlutterAnnotation {
+    var id: String
+}
+
+var annotations: [FlutterAnnotation] = []
+for i in 0..<10000 {
+    annotations.append(FlutterAnnotation(id: "id_\(i)"))
+}
+
+// Ensure the random seed is reproducible for a fair comparison, though time based is ok
+let startArray = Date()
+var count = 0
+for i in 0..<1000 {
+    let id = "id_\(i * 10)"
+    let found = annotations.filter { $0.id == id }.first
+    if found != nil { count += 1 }
+}
+let endArray = Date()
+
+print("Array filter O(N) time: \(endArray.timeIntervalSince(startArray)) seconds for 1000 lookups in 10000 items")
+
+var annotationsMap: [String: FlutterAnnotation] = [:]
+for a in annotations {
+    annotationsMap[a.id] = a
+}
+
+let startDict = Date()
+count = 0
+for i in 0..<1000 {
+    let id = "id_\(i * 10)"
+    let found = annotationsMap[id]
+    if found != nil { count += 1 }
+}
+let endDict = Date()
+
+print("Dict lookup O(1) time: \(endDict.timeIntervalSince(startDict)) seconds for 1000 lookups in 10000 items")

darwin/mapkit_flutter/Sources/mapkit_flutter/Annotations/AnnotationController.swift

@@ -91,9 +91,8 @@ extension MapKitViewHost {
     }
 
     func annotationsToChange(_ annotations: [PlatformAnnotation]) {
-        let oldAnnotations: [MKAnnotation] = self.mapView.annotations
         for annotationData in annotations {
-            if let annotationToChange = oldAnnotations.first(where: { ($0 as? FlutterAnnotation)?.id == annotationData.id }) as? FlutterAnnotation {
+            if let annotationToChange = self.getAnnotation(with: annotationData.id) {
                 let newAnnotation = FlutterAnnotation(fromPlatform: annotationData)
                 if annotationToChange != newAnnotation {
                     if !annotationToChange.wasDragged {
@@ -137,6 +136,7 @@ extension MapKitViewHost {
 
     private func removeAnnotation(id: String) {
         if let flutterAnnotation: FlutterAnnotation = self.getAnnotation(with: id) {
+            self.annotationsById.removeValue(forKey: id)
             self.mapView.removeAnnotation(flutterAnnotation)
         }
     }
@@ -178,7 +178,7 @@ extension MapKitViewHost {
     #endif
 
     private func getAnnotation(with id: String) -> FlutterAnnotation? {
-        return self.mapView.annotations.filter { annotation in return (annotation as? FlutterAnnotation)?.id == id }.first as? FlutterAnnotation
+        return self.annotationsById[id]
     }
 
     private func annotationExists(with id: String) -> Bool {
@@ -193,6 +193,7 @@ extension MapKitViewHost {
         if self.annotationExists(with: annotation.id) {
             self.removeAnnotation(id: annotation.id)
         }
+        self.annotationsById[annotation.id] = annotation
         self.mapView.addAnnotation(annotation)
     }
 

darwin/mapkit_flutter/Sources/mapkit_flutter/MapView/MapKitViewHost.swift

@@ -25,6 +25,7 @@ public class MapKitViewHost: NSObject, @preconcurrency MapKitHostApi {
     var flutterApi: MapKitFlutterApi
     var currentlySelectedAnnotation: String?
     var tileOverlays: [String: FlutterTileOverlay] = [:]
+    var annotationsById: [String: FlutterAnnotation] = [:]
 
     public init(withFrame frame: CGRect, withRegistrar registrar: FlutterPluginRegistrar, withId id: Int64) {
         let suffix = "\(id)"