Adding JSON example. (#1)

jsonexample/lib/dart_convert/converted_complex_object.dart

@@ -0,0 +1,52 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:jsonexample/dart_convert/converted_simple_object.dart';
+
+class ConvertedComplexObject {
+  const ConvertedComplexObject({
+    this.aString,
+    this.anInt,
+    this.aDouble,
+    this.anObject,
+    this.aListOfStrings,
+    this.aListOfInts,
+    this.aListOfDoubles,
+    this.aListOfObjects,
+  });
+
+  final String aString;
+  final int anInt;
+  final double aDouble;
+  final ConvertedSimpleObject anObject;
+  final List<String> aListOfStrings;
+  final List<int> aListOfInts;
+  final List<double> aListOfDoubles;
+  final List<ConvertedSimpleObject> aListOfObjects;
+
+  factory ConvertedComplexObject.fromJson(Map<String, dynamic> json) {
+    if (json == null) return null;
+
+    return ConvertedComplexObject(
+        aString: json['aString'],
+        anInt: json['anInt'],
+        aDouble: json['aDouble'],
+        anObject: json['anObject'] != null
+            ? ConvertedSimpleObject.fromJson(json['anObject'])
+            : null,
+        aListOfStrings: json['aListOfStrings'] != null
+            ? List<String>.from(json['aListOfStrings'])
+            : null,
+        aListOfInts: json['aListOfInts'] != null
+            ? List<int>.from(json['aListOfInts'])
+            : null,
+        aListOfDoubles: json['aListOfDoubles'] != null
+            ? List<double>.from(json['aListOfDoubles'])
+            : null,
+        aListOfObjects: json['aListOfObjects'] != null
+            ? List<ConvertedSimpleObject>.from(json['aListOfObjects']
+                .map((o) => ConvertedSimpleObject.fromJson(o)))
+            : null);
+  }
+}