[objective_c] Swift style KVO pattern (#2344)

Author: liamappelbe

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

@@ -6,6 +6,7 @@
 
 const objCBuiltInInterfaces = {
   'DOBJCDartInputStreamAdapter': 'DartInputStreamAdapter',
+  'DOBJCObservation': 'DOBJCObservation',
   'DOBJCDartProtocolBuilder': 'DartProtocolBuilder',
   'DOBJCDartProtocol': 'DartProtocol',
   'NSArray': 'NSArray',
@@ -109,6 +110,7 @@ const objCBuiltInProtocols = {
   'NSPortDelegate': 'NSPortDelegate',
   'NSSecureCoding': 'NSSecureCoding',
   'NSStreamDelegate': 'NSStreamDelegate',
+  'Observer': 'Observer',
 };
 
 const objCBuiltInCategories = {
@@ -131,5 +133,10 @@ const objCBuiltInCategories = {
 };
 
 const objCBuiltInGlobals = {
+  'NSKeyValueChangeIndexesKey',
+  'NSKeyValueChangeKindKey',
+  'NSKeyValueChangeNewKey',
+  'NSKeyValueChangeNotificationIsPriorKey',
+  'NSKeyValueChangeOldKey',
   'NSLocalizedDescriptionKey',
 };

pkgs/objective_c/CHANGELOG.md

@@ -1,5 +1,8 @@
 ## 8.1.0-wip
 
+- Support the KVO pattern by adding `Observer`, `Observation`, and
+  `NSObject.addObserver`.
+
 ## 8.0.0
 
 - Use ffigen 19.0.0

pkgs/objective_c/ffigen_objc.yaml

@@ -10,6 +10,7 @@ headers:
     - 'src/foundation.h'
     - 'src/input_stream_adapter.h'
     - 'src/ns_number.h'
+    - 'src/observer.h'
     - 'src/protocol.h'
 ffi-native:
 exclude-all-by-default: true
@@ -26,6 +27,7 @@ objc-interfaces:
   # Keep in sync with ffigen's ObjCBuiltInFunctions.builtInInterfaces.
   include:
     - DOBJCDartInputStreamAdapter
+    - DOBJCObservation
     - DOBJCDartProtocolBuilder
     - DOBJCDartProtocol
     - NSArray
@@ -84,6 +86,7 @@ objc-protocols:
     - NSPortDelegate
     - NSSecureCoding
     - NSStreamDelegate
+    - Observer
   rename:
     'NSObject': 'NSObjectProtocol'
 objc-categories:
@@ -157,6 +160,11 @@ enums:
     - NSURLHandleStatus
 globals:
   include:
+    - NSKeyValueChangeIndexesKey
+    - NSKeyValueChangeKindKey
+    - NSKeyValueChangeNewKey
+    - NSKeyValueChangeNotificationIsPriorKey
+    - NSKeyValueChangeOldKey
     - NSLocalizedDescriptionKey
 typedefs:
   include:

pkgs/objective_c/ios/Classes/objective_c.m

@@ -7,4 +7,5 @@
 #include "../../src/input_stream_adapter.m"
 #include "../../src/objective_c.m"
 #include "../../src/objective_c_bindings_generated.m"
+#include "../../src/observer.m"
 #include "../../src/protocol.m"

pkgs/objective_c/lib/objective_c.dart

@@ -29,6 +29,7 @@ export 'src/ns_mutable_data.dart';
 export 'src/ns_number.dart';
 export 'src/ns_string.dart';
 export 'src/objective_c_bindings_exported.dart';
+export 'src/observer.dart';
 export 'src/os_version.dart';
 export 'src/protocol_builder.dart';
 export 'src/selector.dart';

pkgs/objective_c/lib/src/objective_c_bindings_exported.dart

@@ -61,6 +61,11 @@ export 'objective_c_bindings_generated.dart'
         NSItemProviderRepresentationVisibility,
         NSItemProviderWriting,
         NSKeyValueChange,
+        NSKeyValueChangeIndexesKey,
+        NSKeyValueChangeKindKey,
+        NSKeyValueChangeNewKey,
+        NSKeyValueChangeNotificationIsPriorKey,
+        NSKeyValueChangeOldKey,
         NSKeyValueObservingOptions,
         NSKeyValueSetMutationKind,
         NSLinguisticTaggerOptions,
@@ -115,5 +120,6 @@ export 'objective_c_bindings_generated.dart'
         NSURLHandleStatus,
         NSValue,
         NSZone,
+        Observer,
         OpaqueAEDataStorageType,
         Protocol;