Actually use the real type, add parent for data classes

moor/example/example.g.dart

@@ -7,7 +7,7 @@ part of 'example.dart';
 // **************************************************************************
 
 // ignore_for_file: unnecessary_brace_in_string_interps
-class Category {
+class Category extends DataClass {
   final int id;
   final String description;
   Category({this.id, this.description});
@@ -28,6 +28,7 @@ class Category {
       description: json['description'] as String,
     );
   }
+  @override
   Map<String, dynamic> toJson() {
     return {
       'id': id,
@@ -118,7 +119,7 @@ class $CategoriesTable extends Categories
   }
 }
 
-class Recipe {
+class Recipe extends DataClass {
   final int id;
   final String title;
   final String instructions;
@@ -147,6 +148,7 @@ class Recipe {
       category: json['category'] as int,
     );
   }
+  @override
   Map<String, dynamic> toJson() {
     return {
       'id': id,
@@ -276,7 +278,7 @@ class $RecipesTable extends Recipes with TableInfo<$RecipesTable, Recipe> {
   }
 }
 
-class Ingredient {
+class Ingredient extends DataClass {
   final int id;
   final String name;
   final int caloriesPer100g;
@@ -300,6 +302,7 @@ class Ingredient {
       caloriesPer100g: json['caloriesPer100g'] as int,
     );
   }
+  @override
   Map<String, dynamic> toJson() {
     return {
       'id': id,
@@ -412,7 +415,7 @@ class $IngredientsTable extends Ingredients
   }
 }
 
-class IngredientInRecipe {
+class IngredientInRecipe extends DataClass {
   final int recipe;
   final int ingredient;
   final int amountInGrams;
@@ -437,6 +440,7 @@ class IngredientInRecipe {
       amountInGrams: json['amountInGrams'] as int,
     );
   }
+  @override
   Map<String, dynamic> toJson() {
     return {
       'recipe': recipe,

moor/lib/moor.dart

@@ -22,6 +22,7 @@ export 'package:moor/src/runtime/statements/insert.dart';
 export 'package:moor/src/runtime/statements/delete.dart';
 export 'package:moor/src/runtime/structure/columns.dart';
 export 'package:moor/src/runtime/structure/table_info.dart';
+export 'package:moor/src/runtime/data_class.dart';
 export 'package:moor/src/runtime/database.dart';
 export 'package:moor/src/types/sql_types.dart';
 export 'package:moor/src/runtime/migration.dart';

moor/lib/src/runtime/data_class.dart

@@ -0,0 +1,50 @@
+import 'dart:convert';
+
+/// A common supertype for all data classes generated by moor. Data classes are
+/// immutable structures that represent a single row.
+abstract class DataClass {
+  const DataClass();
+
+  // todo better docs, explain ValueSerializer
+
+  /// Converts this object into a representation that can be encoded with
+  /// [json].
+  Map<String, dynamic> toJson(
+      {ValueSerializer serializer = const ValueSerializer.defaults()});
+
+  String toJsonString(
+      {ValueSerializer serializer = const ValueSerializer.defaults()}) {
+    return json.encode(toJson(serializer: serializer));
+  }
+}
+
+/// Serializer responsible for mapping atomic types from and to json.
+abstract class ValueSerializer {
+  const ValueSerializer();
+  const factory ValueSerializer.defaults() = _DefaultValueSerializer;
+
+  dynamic toJson<T>(T value);
+  T fromJson<T>(dynamic json);
+}
+
+class _DefaultValueSerializer extends ValueSerializer {
+  const _DefaultValueSerializer();
+
+  @override
+  T fromJson<T>(json) {
+    if (T == DateTime) {
+      return DateTime.fromMillisecondsSinceEpoch(json as int) as T;
+    }
+
+    return json as T;
+  }
+
+  @override
+  dynamic toJson<T>(T value) {
+    if (value is DateTime) {
+      return value.millisecondsSinceEpoch;
+    }
+
+    return value;
+  }
+}

moor/lib/src/types/sql_types.dart

@@ -113,6 +113,8 @@ class BlobType extends SqlType<Uint8List> {
 }
 
 class RealType extends SqlType<num> {
+  const RealType();
+
   @override
   num mapFromDatabaseResponse(response) => response as num;
 

moor/lib/src/types/type_system.dart

@@ -13,7 +13,8 @@ class SqlTypeSystem {
           StringType(),
           IntType(),
           DateTimeType(),
-          BlobType()
+          BlobType(),
+          RealType(),
         ]);
 
   /// Returns the appropriate sql type for the dart type provided as the

moor/test/data/tables/todos.g.dart

@@ -7,7 +7,7 @@ part of 'todos.dart';
 // **************************************************************************
 
 // ignore_for_file: unnecessary_brace_in_string_interps
-class TodoEntry {
+class TodoEntry extends DataClass {
   final int id;
   final String title;
   final String content;
@@ -42,6 +42,7 @@ class TodoEntry {
       category: json['category'] as int,
     );
   }
+  @override
   Map<String, dynamic> toJson() {
     return {
       'id': id,
@@ -199,7 +200,7 @@ class $TodosTableTable extends TodosTable
   }
 }
 
-class Category {
+class Category extends DataClass {
   final int id;
   final String description;
   Category({this.id, this.description});
@@ -220,6 +221,7 @@ class Category {
       description: json['description'] as String,
     );
   }
+  @override
   Map<String, dynamic> toJson() {
     return {
       'id': id,
@@ -307,7 +309,7 @@ class $CategoriesTable extends Categories
   }
 }
 
-class User {
+class User extends DataClass {
   final int id;
   final String name;
   final bool isAwesome;
@@ -347,6 +349,7 @@ class User {
       creationTime: json['creationTime'] as DateTime,
     );
   }
+  @override
   Map<String, dynamic> toJson() {
     return {
       'id': id,
@@ -499,7 +502,7 @@ class $UsersTable extends Users with TableInfo<$UsersTable, User> {
   }
 }
 
-class SharedTodo {
+class SharedTodo extends DataClass {
   final int todo;
   final int user;
   SharedTodo({this.todo, this.user});
@@ -518,6 +521,7 @@ class SharedTodo {
       user: json['user'] as int,
     );
   }
+  @override
   Map<String, dynamic> toJson() {
     return {
       'todo': todo,
@@ -611,7 +615,7 @@ class $SharedTodosTable extends SharedTodos
   }
 }
 
-class TableWithoutPKData {
+class TableWithoutPKData extends DataClass {
   final int notReallyAnId;
   final num someFloat;
   TableWithoutPKData({this.notReallyAnId, this.someFloat});
@@ -634,6 +638,7 @@ class TableWithoutPKData {
       someFloat: json['someFloat'] as num,
     );
   }
+  @override
   Map<String, dynamic> toJson() {
     return {
       'notReallyAnId': notReallyAnId,

moor_generator/lib/src/writer/data_class_writer.dart

@@ -10,7 +10,7 @@ class DataClassWriter {
   DataClassWriter(this.table);
 
   void writeInto(StringBuffer buffer) {
-    buffer.write('class ${table.dartTypeName} {\n');
+    buffer.write('class ${table.dartTypeName} extends DataClass {\n');
 
     // write individual fields
     for (var column in table.columns) {
@@ -115,7 +115,7 @@ class DataClassWriter {
   }
 
   void _writeToJson(StringBuffer buffer) {
-    buffer.write('Map<String, dynamic> toJson() {\n return {');
+    buffer.write('@override Map<String, dynamic> toJson() {\n return {');
 
     for (var column in table.columns) {
       final getter = column.dartGetterName;