some fixes for PR comments

packages/webview_flutter/webview_flutter_wkwebview/example/ios/RunnerTests/FWFNavigationDelegateHostApiTests.m

@@ -11,7 +11,7 @@
 // Used to test that a FlutterBinaryMessenger with a strong reference to a host api won't
 // lead to a circular reference.
 @interface FWFTestMessenger : NSObject <FlutterBinaryMessenger>
-@property(strong, nullable) id hostApi;
+@property(strong, nullable) id hostAPI;
 @end
 
 @implementation FWFTestMessenger
@@ -39,12 +39,12 @@ @interface FWFNavigationDelegateHostApiTests : XCTestCase
 @implementation FWFNavigationDelegateHostApiTests
 - (void)testCreateWithIdentifier {
   FWFInstanceManager *instanceManager = [[FWFInstanceManager alloc] init];
-  FWFNavigationDelegateHostApiImpl *hostApi = [[FWFNavigationDelegateHostApiImpl alloc]
+  FWFNavigationDelegateHostApiImpl *hostAPI = [[FWFNavigationDelegateHostApiImpl alloc]
       initWithBinaryMessenger:OCMProtocolMock(@protocol(FlutterBinaryMessenger))
               instanceManager:instanceManager];
 
   FlutterError *error;
-  [hostApi createWithIdentifier:@0 error:&error];
+  [hostAPI createWithIdentifier:@0 error:&error];
   FWFNavigationDelegate *navigationDelegate =
       (FWFNavigationDelegate *)[instanceManager instanceForIdentifier:0];
 
@@ -54,12 +54,12 @@ - (void)testCreateWithIdentifier {
 
 - (void)testDidFinishNavigation {
   FWFInstanceManager *instanceManager = [[FWFInstanceManager alloc] init];
-  FWFNavigationDelegateHostApiImpl *hostApi = [[FWFNavigationDelegateHostApiImpl alloc]
+  FWFNavigationDelegateHostApiImpl *hostAPI = [[FWFNavigationDelegateHostApiImpl alloc]
       initWithBinaryMessenger:OCMProtocolMock(@protocol(FlutterBinaryMessenger))
               instanceManager:instanceManager];
 
   FlutterError *error;
-  [hostApi createWithIdentifier:@0 error:&error];
+  [hostAPI createWithIdentifier:@0 error:&error];
   FWFNavigationDelegate *navigationDelegate =
       (FWFNavigationDelegate *)[instanceManager instanceForIdentifier:0];
   id mockDelegate = OCMPartialMock(navigationDelegate);
@@ -85,14 +85,14 @@ - (void)testDidFinishNavigation {
 - (void)testInstanceCanBeReleasedWhenInstanceManagerIsReleased {
   FWFTestMessenger *testMessenger = [[FWFTestMessenger alloc] init];
   FWFInstanceManager *instanceManager = [[FWFInstanceManager alloc] init];
-  FWFNavigationDelegateHostApiImpl *hostApi =
+  FWFNavigationDelegateHostApiImpl *hostAPI =
       [[FWFNavigationDelegateHostApiImpl alloc] initWithBinaryMessenger:testMessenger
                                                         instanceManager:instanceManager];
 
-  testMessenger.hostApi = hostApi;
+  testMessenger.hostAPI = hostAPI;
 
   FlutterError *error;
-  [hostApi createWithIdentifier:@0 error:&error];
+  [hostAPI createWithIdentifier:@0 error:&error];
   FWFNavigationDelegate __weak *navigationDelegate =
       (FWFNavigationDelegate *)[instanceManager instanceForIdentifier:0];
 

packages/webview_flutter/webview_flutter_wkwebview/lib/src/common/instance_manager.dart

@@ -4,8 +4,17 @@
 
 /// Maintains instances stored to communicate with Objective-C objects.
 class InstanceManager {
-  final Map<int, Object> _instanceIdsToInstances = <int, Object>{};
-  final Expando<Object> _instancesToInstanceIds = Expando<Object>();
+  // Instances that the manager wants to maintain a strong reference to.
+  final Map<int, Object> _strongInstances = <int, Object>{};
+  // Expando is used because it doesn't prevent its keys from becoming
+  // inaccessible. This allows the manager to efficiently retrieve an instance
+  // id of an object without holding a strong reference to the object.
+  //
+  // It also doesn't use `==` to search for instance ids, which would lead to an
+  // infinite loop when comparing an object to its copy. (i.e. which is caused
+  // by calling instanceManager.getInstanceId() inside of `==` while this was a
+  // HashMap).
+  final Expando<int> _instanceIds = Expando<int>();
 
   int _nextInstanceId = 0;
 
@@ -22,15 +31,15 @@ class InstanceManager {
     }
 
     final int instanceId = _nextInstanceId++;
-    _instancesToInstanceIds[instance] = instanceId;
-    _instanceIdsToInstances[instanceId] = instance;
+    _instanceIds[instance] = instanceId;
+    _strongInstances[instanceId] = instance;
     return instanceId;
   }
 
   /// Store a copy of an instance with the same instance id.
   void addCopy(Object original, Object copy) {
     assert(original.runtimeType == copy.runtimeType);
-    _instancesToInstanceIds[copy] = _instancesToInstanceIds[original];
+    _instanceIds[copy] = _instanceIds[original];
     assert(original == copy);
   }
 
@@ -39,21 +48,21 @@ class InstanceManager {
   /// Returns null if the instance is removed. Otherwise, return the instanceId
   /// of the removed instance.
   int? removeInstance<T extends Object>(T instance) {
-    final int? instanceId = _instancesToInstanceIds[instance] as int?;
+    final int? instanceId = _instanceIds[instance];
     if (instanceId != null) {
-      _instancesToInstanceIds[instance] = null;
-      _instanceIdsToInstances.remove(instanceId);
+      _instanceIds[instance] = null;
+      _strongInstances.remove(instanceId);
     }
     return instanceId;
   }
 
   /// Retrieve the Object paired with instanceId.
   T? getInstance<T extends Object>(int instanceId) {
-    return _instanceIdsToInstances[instanceId] as T?;
+    return _strongInstances[instanceId] as T?;
   }
 
   /// Retrieve the instanceId paired with instance.
   int? getInstanceId(Object instance) {
-    return _instancesToInstanceIds[instance] as int?;
+    return _instanceIds[instance];
   }
 }

packages/webview_flutter/webview_flutter_wkwebview/lib/src/web_kit/web_kit_api_impls.dart

@@ -588,10 +588,9 @@ class WKNavigationDelegateFlutterApiImpl
     int webViewInstanceId,
     String? url,
   ) {
-    _getDelegate(instanceId).didFinishNavigation!(
-      instanceManager.getInstance(webViewInstanceId)!,
-      url,
-    );
+    final void Function(WKWebView, String?)? function =
+        _getDelegate(instanceId).didFinishNavigation;
+    function?.call(instanceManager.getInstance(webViewInstanceId)!, url);
   }
 }