CODEWITHSUNDEEP
androidrealmrealm-list
Weizhi
Weizhi

Reputation: 1037

RealmList in RealmObject. How to persist order?

I have a RealmObject with a RealmList as one of its field.

public class ToyMaker extends RealmObject {
    private RealmList<Toy> toyList;
    ...
}

public class Toy extends RealmObject {
    ...
}

  1. Will the ordering of Toy in toyList be persisted when written to Realm and reading it back?

  2. If ordering is not persisted by Realm, how can i achieve this manually given that

    A. I cannot add additional fields (e.g. index) in Toy class (a Toy can have many ToyMaker so an index field in Toy is not feasible.

    B. The ordering is in the order that Toy is added to toyList.

Upvotes: 3

Views: 2238

Answers (1)

Christian Melchior
Christian Melchior

Reputation: 20126

A RealmList is ordered, so case #1 is correct. Just add them in the order you want, and that order will be persisted.

In general though, ordering is not guaranteed, so creating 2 objects in the Realm does not imply an order:

realm.createObject(Person.class, 1);
realm.createObject(Person.class, 2);

// Doing this is not guaranteed to return Person:1
realm.where(Person.class).findAll().first()

// Always use a sort in queries if you want a specific order
realm.where(Person.class).findAllSorted("id", Sort.ASCENDING).first();

Upvotes: 6

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