Anotaciones de propiedad - Flutter SDK

Required and Optional Properties

En Dart, los tipos de valor son implícitamente no nulos, pero pueden hacerse opcionales (nulos) añadiendo ?. Incluir ? Hacer que las propiedades sean opcionales.

class _Vehicle {
  @PrimaryKey()
  late ObjectId id;
  late String? maybeDescription; // optional value
  late double milesTravelled = 0; // 0 is default value
  @Ignored()
  late String notInRealmModel;
  @Indexed()
  late String make;
  @MapTo('wheels') // 'wheels' is property name in the RealmObject
  late int numberOfWheels;
}

Default Field Values

Puedes usar las funcionalidades incorporadas del lenguaje para asignar un valor por defecto a una propiedad. Asigna un valor por defecto en la declaración de la propiedad.

class _Vehicle {
  @PrimaryKey()
  late ObjectId id;
  late String? maybeDescription; // optional value
  late double milesTravelled = 0; // 0 is default value
  @Ignored()
  late String notInRealmModel;
  @Indexed()
  late String make;
  @MapTo('wheels') // 'wheels' is property name in the RealmObject
  late int numberOfWheels;
}

llave primaria

La anotación PrimaryKey indica una propiedad de clave primaria. La clave primaria es un identificador único para un objeto en un realm. No puede haber otros objetos del mismo tipo que compartan la clave primaria de un objeto.

Important aspects of primary keys:

• No se puede cambiar una llave primaria después de agregar un objeto a un realm.

• Only add a primary key to one property in a RealmModel.

• Only String, int, ObjectId, and Uuid types can be primary keys.

• Realm automatically indexes primary keys.

• Primary keys are nullable. null can only be the primary key of one object in a collection.

class _Vehicle {
  @PrimaryKey()
  late ObjectId id;
  late String? maybeDescription; // optional value
  late double milesTravelled = 0; // 0 is default value
  @Ignored()
  late String notInRealmModel;
  @Indexed()
  late String make;
  @MapTo('wheels') // 'wheels' is property name in the RealmObject
  late int numberOfWheels;
}

Map a Property or Class to a Different Name

The MapTo annotation indicates that a model or property should be persisted under a different name. It's useful when opening a Realm across different bindings where code style conventions can differ. For example:

• Para facilitar el trabajo entre plataformas donde las convenciones de nomenclatura difieren. Por ejemplo, si los nombres de las propiedades del esquema de Device Sync usan snake case, mientras que tu proyecto usa camel case.

• To change a class or field name without forcing a migration.

@RealmModel()
@MapTo('naval_ship')
class _Boat {
  @PrimaryKey()
  late ObjectId id;
  late String name;
  late int? maxKnots;
  late int? nauticalMiles;
}

class _Vehicle {
  @PrimaryKey()
  late ObjectId id;
  late String? maybeDescription; // optional value
  late double milesTravelled = 0; // 0 is default value
  @Ignored()
  late String notInRealmModel;
  @Indexed()
  late String make;
  @MapTo('wheels') // 'wheels' is property name in the RealmObject
  late int numberOfWheels;
}

Ignore Properties from Realm Schema

If you add the Ignored annotation to a property in your RealmModel, the realm object generator doesn't include the property in the RealmObject schema or persist it to Realm.

class _Vehicle {
  @PrimaryKey()
  late ObjectId id;
  late String? maybeDescription; // optional value
  late double milesTravelled = 0; // 0 is default value
  @Ignored()
  late String notInRealmModel;
  @Indexed()
  late String make;
  @MapTo('wheels') // 'wheels' is property name in the RealmObject
  late int numberOfWheels;
}

Propiedades del índice

Add the Indexed annotation to create an index on the field. Indexes can greatly speed up some queries at the cost of slightly slower write times and additional storage and memory overhead. Realm stores indexes on disk, which makes your realm files larger. Each index entry is a minimum of 12 bytes. Indexes can be nullable.

Se pueden indexar los siguientes tipos de datos:

• bool

• int

• String

• ObjectId

• Uuid

• DateTime

• RealmValue

class _Vehicle {
  @PrimaryKey()
  late ObjectId id;
  late String? maybeDescription; // optional value
  late double milesTravelled = 0; // 0 is default value
  @Ignored()
  late String notInRealmModel;
  @Indexed()
  late String make;
  @MapTo('wheels') // 'wheels' is property name in the RealmObject
  late int numberOfWheels;
}

@RealmModel()
class _Rug {
    @PrimaryKey()
    late ObjectId id;
    @Indexed(RealmIndexType.fullText)
    late String pattern;
    @Indexed(RealmIndexType.fullText)
    late String material;
    late int softness;
}