[Pigeon] Fix Obj-C generation cast bug (#375)

packages/pigeon/lib/objc_generator.dart

@@ -446,7 +446,7 @@ static NSDictionary<NSString*, id>* wrapResult(NSDictionary *result, FlutterErro
       for (final Field field in klass.fields) {
         if (enumNames.contains(field.dataType)) {
           indent.writeln(
-              '$resultName.${field.name} = (int)${_dictGetter(classNames, 'dict', field, options.prefix)};');
+              '$resultName.${field.name} = [${_dictGetter(classNames, 'dict', field, options.prefix)} integerValue];');
         } else {
           indent.writeln(
               '$resultName.${field.name} = ${_dictGetter(classNames, 'dict', field, options.prefix)};');

packages/pigeon/test/objc_generator_test.dart

@@ -69,6 +69,36 @@ void main() {
     expect(code, contains('  PREFIXEnum1Two = 1,'));
   });
 
+  test('gen one class source with enum', () {
+    final Root root = Root(
+      apis: <Api>[],
+      classes: <Class>[
+        Class(
+          name: 'Foobar',
+          fields: <Field>[
+            Field(name: 'field1', dataType: 'String'),
+            Field(name: 'enum1', dataType: 'Enum1'),
+          ],
+        ),
+      ],
+      enums: <Enum>[
+        Enum(
+          name: 'Enum1',
+          members: <String>[
+            'one',
+            'two',
+          ],
+        )
+      ],
+    );
+    final StringBuffer sink = StringBuffer();
+    generateObjcSource(ObjcOptions(header: 'foo.h'), root, sink);
+    final String code = sink.toString();
+    expect(code, contains('#import "foo.h"'));
+    expect(code, contains('@implementation Foobar'));
+    expect(code, contains('result.enum1 = [dict[@"enum1"] integerValue];'));
+  });
+
   test('gen one api header', () {
     final Root root = Root(apis: <Api>[
       Api(name: 'Api', location: ApiLocation.host, methods: <Method>[