Add a `toJson` method for serialization.

moor_flutter/example/lib/database/database.g.dart

@@ -23,6 +23,15 @@ class TodoEntry {
       category: intType.mapFromDatabaseResponse(data['category']),
     );
   }
+  Map<String, Object> toJson() {
+    return {
+      'id': id,
+      'content': content,
+      'targetDate': targetDate,
+      'category': category,
+    };
+  }
+
   TodoEntry copyWith(
           {int id, String content, DateTime targetDate, int category}) =>
       TodoEntry(
@@ -128,6 +137,13 @@ class Category {
       description: stringType.mapFromDatabaseResponse(data['`desc`']),
     );
   }
+  Map<String, Object> toJson() {
+    return {
+      'id': id,
+      'description': description,
+    };
+  }
+
   Category copyWith({int id, String description}) => Category(
         id: id ?? this.id,
         description: description ?? this.description,

moor_generator/lib/src/writer/data_class_writer.dart

@@ -26,6 +26,9 @@ class DataClassWriter {
     // Also write parsing factory
     _writeMappingConstructor(buffer);
 
+    // And a serializer method
+    _writeToJson(buffer);
+
     // And a convenience method to copy data from this class.
     _writeCopyWith(buffer);
 
@@ -94,6 +97,17 @@ class DataClassWriter {
     buffer.write(');}\n');
   }
 
+  void _writeToJson(StringBuffer buffer) {
+    buffer.write('Map<String, Object> toJson() {\n return {');
+
+    for (var column in table.columns) {
+      final getter = column.dartGetterName;
+      buffer.write('\'$getter\': $getter,');
+    }
+
+    buffer.write('};}');
+  }
+
   void _writeCopyWith(StringBuffer buffer) {
     final dataClassName = table.dartTypeName;