[objective_c] Add NSNull (#2628)

Author: liamappelbe

pkgs/ffigen/lib/src/code_generator/objc_built_in_types.dart

@@ -36,6 +36,7 @@ const objCBuiltInInterfaces = {
   'NSMutableSet': 'NSMutableSet',
   'NSMutableString': 'NSMutableString',
   'NSNotification': 'NSNotification',
+  'NSNull': 'NSNull',
   'NSNumber': 'NSNumber',
   'NSObject': 'NSObject',
   'NSOutputStream': 'NSOutputStream',

pkgs/objective_c/CHANGELOG.md

@@ -3,7 +3,9 @@
 - Use ffigen 20.0.0
 - Fix missing `NSNumber` category includes in iOS and macOS `objective_c.m`
   files.
-- Add `NSBundle` to the bindings.
+- Add `NSBundle` and `NSNull` to the bindings.
+- Fix a [bug](https://github.com/dart-lang/native/issues/2627) where
+  `NSMutableDictionary.of` returned a `NSDictionary`.
 
 ## 8.1.0
 

pkgs/objective_c/ffigen_objc.yaml

@@ -56,6 +56,7 @@ objc-interfaces:
     - NSMutableSet
     - NSMutableString
     - NSNotification
+    - NSNull
     - NSNumber
     - NSObject
     - NSOutputStream

pkgs/objective_c/lib/src/converter.dart

@@ -19,9 +19,10 @@ ObjCObjectBase _defaultObjCConverter(Object o) =>
 /// If [dartObject] is not one of the recognized types, [convertOther] is
 /// called. If [convertOther] is not provided, an error is thrown.
 ObjCObjectBase toObjCObject(
-  Object dartObject, {
+  Object? dartObject, {
   ObjCObjectBase Function(Object) convertOther = _defaultObjCConverter,
 }) => switch (dartObject) {
+  null => NSNull.null$(),
   ObjCObjectBase() => dartObject,
   num() => dartObject.toNSNumber(),
   String() => dartObject.toNSString(),
@@ -99,6 +100,20 @@ Object toDartObject(
   return convertOther(objCObject);
 }
 
+/// Converts a Objective C object to the corresponding Dart object.
+///
+/// See [toDartObject]. This method will additionally return `null` if passed an
+/// `NSNull`.
+Object? toNullableDartObject(
+  ObjCObjectBase objCObject, {
+  Object Function(ObjCObjectBase) convertOther = _defaultDartConverter,
+}) {
+  if (NSNull.isInstance(objCObject)) {
+    return null;
+  }
+  return toDartObject(objCObject, convertOther: convertOther);
+}
+
 extension NSArrayToDartList on NSArray {
   List<Object> toDartList({
     Object Function(ObjCObjectBase) convertOther = _defaultDartConverter,

pkgs/objective_c/lib/src/objective_c_bindings_exported.dart

@@ -116,6 +116,8 @@ export 'objective_c_bindings_generated.dart'
         NSMutableString$Methods,
         NSNotification,
         NSNotification$Methods,
+        NSNull,
+        NSNull$Methods,
         NSNumber,
         NSNumber$Methods,
         NSNumberCreation,

pkgs/objective_c/lib/src/objective_c_bindings_generated.dart

@@ -11564,7 +11564,7 @@ extension NSMutableData$Methods on NSMutableData {
 /// NSMutableDictionary
 class NSMutableDictionary extends NSDictionary {
   /// Creates a [NSMutableDictionary] from [other].
-  static NSDictionary of(Map<NSCopying, objc.ObjCObjectBase> other) =>
+  static NSMutableDictionary of(Map<NSCopying, objc.ObjCObjectBase> other) =>
       NSMutableDictionary.dictionaryWithCapacity(other.length)..addAll(other);
 
   /// Creates a [NSMutableDictionary] from [entries].
@@ -13880,6 +13880,126 @@ extension NSNotification$Methods on NSNotification {
   }
 }
 
+/// NSNull
+class NSNull extends NSObject implements NSCopying, NSSecureCoding {
+  NSNull._(
+    ffi.Pointer<objc.ObjCObject> pointer, {
+    bool retain = false,
+    bool release = false,
+  }) : super.castFromPointer(pointer, retain: retain, release: release);
+
+  /// Constructs a [NSNull] that points to the same underlying object as [other].
+  NSNull.castFrom(objc.ObjCObjectBase other)
+    : this._(other.ref.pointer, retain: true, release: true);
+
+  /// Constructs a [NSNull] that wraps the given raw object pointer.
+  NSNull.castFromPointer(
+    ffi.Pointer<objc.ObjCObject> other, {
+    bool retain = false,
+    bool release = false,
+  }) : this._(other, retain: retain, release: release);
+
+  /// Returns whether [obj] is an instance of [NSNull].
+  static bool isInstance(objc.ObjCObjectBase obj) {
+    return _objc_msgSend_19nvye5(
+      obj.ref.pointer,
+      _sel_isKindOfClass_,
+      _class_NSNull,
+    );
+  }
+
+  /// alloc
+  static NSNull alloc() {
+    final _ret = _objc_msgSend_151sglz(_class_NSNull, _sel_alloc);
+    return NSNull.castFromPointer(_ret, retain: false, release: true);
+  }
+
+  /// allocWithZone:
+  static NSNull allocWithZone(ffi.Pointer<NSZone> zone) {
+    final _ret = _objc_msgSend_1cwp428(
+      _class_NSNull,
+      _sel_allocWithZone_,
+      zone,
+    );
+    return NSNull.castFromPointer(_ret, retain: false, release: true);
+  }
+
+  /// new
+  static NSNull new$() {
+    final _ret = _objc_msgSend_151sglz(_class_NSNull, _sel_new);
+    return NSNull.castFromPointer(_ret, retain: false, release: true);
+  }
+
+  /// null
+  static NSNull null$() {
+    final _ret = _objc_msgSend_151sglz(_class_NSNull, _sel_null);
+    return NSNull.castFromPointer(_ret, retain: true, release: true);
+  }
+
+  /// supportsSecureCoding
+  static bool getSupportsSecureCoding() {
+    return _objc_msgSend_91o635(_class_NSNull, _sel_supportsSecureCoding);
+  }
+
+  /// Returns a new instance of NSNull constructed with the default `new` method.
+  factory NSNull() => new$();
+}
+
+extension NSNull$Methods on NSNull {
+  /// autorelease
+  NSNull autorelease() {
+    final _ret = _objc_msgSend_151sglz(this.ref.pointer, _sel_autorelease);
+    return NSNull.castFromPointer(_ret, retain: true, release: true);
+  }
+
+  /// encodeWithCoder:
+  void encodeWithCoder(NSCoder coder) {
+    _objc_msgSend_xtuoz7(
+      this.ref.pointer,
+      _sel_encodeWithCoder_,
+      coder.ref.pointer,
+    );
+  }
+
+  /// init
+  NSNull init() {
+    objc.checkOsVersionInternal(
+      'NSNull.init',
+      iOS: (false, (2, 0, 0)),
+      macOS: (false, (10, 0, 0)),
+    );
+    final _ret = _objc_msgSend_151sglz(
+      this.ref.retainAndReturnPointer(),
+      _sel_init,
+    );
+    return NSNull.castFromPointer(_ret, retain: false, release: true);
+  }
+
+  /// initWithCoder:
+  NSNull? initWithCoder(NSCoder coder) {
+    final _ret = _objc_msgSend_1sotr3r(
+      this.ref.retainAndReturnPointer(),
+      _sel_initWithCoder_,
+      coder.ref.pointer,
+    );
+    return _ret.address == 0
+        ? null
+        : NSNull.castFromPointer(_ret, retain: false, release: true);
+  }
+
+  /// retain
+  NSNull retain() {
+    final _ret = _objc_msgSend_151sglz(this.ref.pointer, _sel_retain);
+    return NSNull.castFromPointer(_ret, retain: true, release: true);
+  }
+
+  /// self
+  NSNull self() {
+    final _ret = _objc_msgSend_151sglz(this.ref.pointer, _sel_self);
+    return NSNull.castFromPointer(_ret, retain: true, release: true);
+  }
+}
+
 /// NSNumber
 class NSNumber extends NSValue {
   NSNumber._(
@@ -36253,6 +36373,7 @@ late final _class_NSMutableOrderedSet = objc.getClass("NSMutableOrderedSet");
 late final _class_NSMutableSet = objc.getClass("NSMutableSet");
 late final _class_NSMutableString = objc.getClass("NSMutableString");
 late final _class_NSNotification = objc.getClass("NSNotification");
+late final _class_NSNull = objc.getClass("NSNull");
 late final _class_NSNumber = objc.getClass("NSNumber");
 late final _class_NSObject = objc.getClass("NSObject");
 late final _class_NSOrderedCollectionChange = objc.getClass(
@@ -41752,6 +41873,7 @@ late final _sel_notificationWithName_object_ = objc.registerName(
 late final _sel_notificationWithName_object_userInfo_ = objc.registerName(
   "notificationWithName:object:userInfo:",
 );
+late final _sel_null = objc.registerName("null");
 late final _sel_numberOfArguments = objc.registerName("numberOfArguments");
 late final _sel_numberWithBool_ = objc.registerName("numberWithBool:");
 late final _sel_numberWithChar_ = objc.registerName("numberWithChar:");

pkgs/objective_c/test/converter_test.dart

@@ -24,6 +24,10 @@ void main() {
       final obj = NSObject();
       expect(toObjCObject(obj), obj);
 
+      // NSNull.null$() is a singleton.
+      expect(toObjCObject(null), NSNull.null$());
+      expect(toNullableDartObject(NSNull.null$()), null);
+
       expect(toObjCObject(123), isA<NSNumber>());
       expect((toObjCObject(123) as NSNumber).longLongValue, 123);
       expect(toDartObject(toObjCObject(123)), isA<int>());

pkgs/objective_c/tool/data/extra_methods.dart.in

@@ -153,7 +153,7 @@ class NSDictionary with MapBase<NSCopying, objc.ObjCObjectBase> {
 
 class NSMutableDictionary {
   /// Creates a [NSMutableDictionary] from [other].
-  static NSDictionary of(Map<NSCopying, objc.ObjCObjectBase> other) =>
+  static NSMutableDictionary of(Map<NSCopying, objc.ObjCObjectBase> other) =>
       NSMutableDictionary.dictionaryWithCapacity(other.length)..addAll(other);
 
   /// Creates a [NSMutableDictionary] from [entries].