Records topic

Record Fields

dart_mappable supports record fields out of the box. When you define a class, any field using a record type will be automatically included in the serialization.

@MappableClass()
class Location with LocationMappable {
  
  const Location({
    required this.name,
    required this.coordinates, 
  });

  final (String, String) name;
  final ({double lat, double lng}) coordinates;
}

An instance of this class would be encoded to:

{
  "name": {
    "$1": "John",
    "$2": "Doe"
  },
  "coordinates": {
    "lat": 123,
    "lng": 456
  }
}

Record Aliases

Additionally, you can create record type aliases using annotated typedefs:

@MappableRecord()
typedef Coordinates = ({double lat, double lng});

When using this type for a field of another class, it will be serialized as expected.

This also allows you to serialize records using the standalone generated mapper class as well as the generated extension methods:

void main() {
  // Using the generated mapper class.
  Coordinates coords  = CoordinatesMapper.fromJson('{"lat": 123, "lng": 456}');
  
  // Using the generated extension methods.
  String json = coords.toJson();
}

Renaming Record Properties

You can also annotate individual fields of a record alias to change the key or add a hook:

@MappableRecord()
typedef FullName = (@MappableField(key: 'firstName') String, @MappableField(hook: MyHook()) String);

This will only work on annotated record type aliases, not inline record fields.

Note: Since typedefs are just an alias for a type, you cannot define two aliases for the same type with different @MappableField() modifiers. Only one will be used for serialization.

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Next: Configuration

Classes

MappableField

Used to annotate a parameter or field to overwrite the mapped key.

MappableRecord

Used to annotate a record in order to generate mapping code.