Annotation Type LinkingObjects

io.realm.annotations

Implemented interfaces:

• java.lang.annotation.Annotation

Annotation for defining a reverse relationship from one class to another. This annotation can only be added to a field of the type RealmResults .

To expose reverse relationships for use, create a declaration as follows:

public class Person extends RealmObject {
  String name;
  Dog dog; // Normal relation
}
public class Dog extends RealmObject {
  // This holds all Person objects with a relation to this Dog object (= linking objects)
  @LinkingObjects("dog")
  final RealmResults<Person> owners = null;
}
// Find all Dogs with at least one owner named John
realm.where(Dog.class).equalTo("owners.name", "John").findAll();

In the above example `Person` is related to `Dog` through the field `dog`. This in turn means that an implicit reverse relationship exists between the class `Dog` and the class `Person`. This inverse relationship is made public and queryable by the `RealmResults` field annotated with `@LinkingObject`. This makes it possible to query properties of the dogs owner without having to manually maintain a "owner" field in the `Dog` class.Linking objects have the following properties:

• El enlace lo mantiene Realm y solo funciona para objetos administrados.

• Se pueden hacer querys como una relación normal.

• They can be followed just like normal relation.

• Se ignoran cuando se realiza un `copyToRealm().`

• Se ignoran cuando se realiza un `copyFromRealm().`

• They are ignored when using the various `createObjectFromJson*` and `createAllFromJson*` methods.

• Listeners on an object with a `@LinkingObject` field will not be triggered if the linking objects change, e.g: if another object drops a reference to this object.

In addition, they have the following restrictions:

• @Ignore takes precedence. A @LinkingObjects annotation on @Ignore field will be ignored.

• The annotated field cannot be @Required.

• The annotated field must be `final`.

• The annotation argument (the name of the backlinked field) is required.

• The annotation argument must be a simple field name. It cannot contain periods ('.').

• The annotated field must be of type `RealmResults<T>` where T is concrete class that extends `RealmModel`.

Tenga en cuenta que cuando la fuente de la referencia inversa ("perro" en el ejemplo anterior) es una `Lista`, existe una referencia inversa para cada referencia hacia adelante, incluso si ambas referencias hacia adelante apuntan al mismo objeto. Si la clase `Person` anterior se definiera como:

  public class DogLover extends RealmObject {
   String name;
   List<Dog> dogs = new ArrayList<Dog>;
   }
then the following code executes without error

Dog fido = new Dog();
 DogLover john = new DogLover()
 john.dogs.add(fido);
 john.dogs.add(fido);
 assert john.dogs.size() == 2;
 assert fido.owners.size() == 2;

Consultar una relación inversa es como consultar cualquier RealmResults . Esto significa que una relación inversa no puede ser null, pero puede estar vacía (longitud 0). Es posible consultar campos en la clase fuente. Esto es equivalente a las consultas de enlace. Lea

para obtener más información .

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