Add example

example/builder/main.dart

@@ -28,6 +28,7 @@ import './src/function_component.dart' as function;
 import 'src/functional_consumed_props.dart';
 import 'src/new_class_consumed_props.dart';
 import 'src/nullability.dart';
+import 'src/partial.dart' as partial;
 
 class ExampleState {
   final String testValue;
@@ -85,6 +86,7 @@ main() {
       )
       ), querySelector('#content')
   );
+  partial.partialExample();
 }
 
 final componentConstructorsByName = <String, Map Function()>{

example/builder/src/partial.dart

@@ -0,0 +1,48 @@
+// Copyright 2023 Workiva Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'package:over_react/over_react.dart';
+
+part 'partial.over_react.g.dart';
+
+UiFactory<RequiredTestProps> RequiredTest = castUiFactory(_$RequiredTest);
+
+mixin RequiredTestProps on UiProps {
+  late String testRequiredProp;
+}
+
+void partialExample() {
+  // An empty props map
+  final partialProps = RequiredTest();
+
+  try {
+    // Throws: "Expected a value of type 'String', but got one of type 'Null'",
+    // because the prop is non-nullable and required, but not present in the map.
+    print(partialProps.testRequiredProp);
+  } catch (e) {
+    print('Threw: $e');
+  }
+
+  // APIs for safely accessing required props:
+
+  // 'default'
+  print(partialProps.getRequiredProp((p) => p.testRequiredProp, orElse: () => 'default'));
+  // null
+  print(partialProps.getRequiredPropOrNull((p) => p.testRequiredProp));
+
+  // Bonus added API: UiProps.getPropKey:
+
+  // 'NullabilityPropsMixin.testRequiredProp'
+  print(partialProps.getPropKey((p) => p.testRequiredProp));
+}