如何正确保存包含RealmList的对象？

Question

I have 2 realm objects: Unit and Subunit. Unit object has a realm list of subunits. I work with single Unit object. Periodically a new Subunit object is created and added to Unit's list, and then I call copyToRealmOrUpdate on my Unit object. However, every time I call copyToRealmOrUpdate, all the Subunits that Unit contains get copied again even if they already exist in database. This causes my database to grow in size quickly. Is there a way to save only last Subunit that was added to list every time I save Unit object? Thanks

Answer 1

Try this code for creating new Subunit instances:

realm.beginTransaction();

Unit unit = realm.where(Unit.class)
                 // write your condition for extracting of Unit object
                 .equalTo("id", unit_id).findFirst();

if(unit == null){
    Log.e(APP_TAG, "Unit " + unit_id + " not found");
    realm.cancelTransaction();
    return;
}

Subunit subunit = realm.createObject(Subunit.class);
// setup subunit fields

unit.getSubunits().add(subunit);

realm.commitTransaction();

Instead of creating Unit object every time your need to get this from realm by particular query and put Subunit instance directly to query object.

Answer 2

1. Create one Unit -Object and save it with copyToRealmOrUpdate in database.
2. When you create new Subunit , save him with copyToRealmOrUpdate in database.
3. Then you can call Unit -Object, that is already saved in database, and with Unit.getSubunits().add(Subunit) you add saved Subunit in database to saved Unit in database.

You don't need save Unit many times in database.