io.realm

Interface RealmMigration

public interface RealmMigration

The RealmMigration class is used to describe the migration of one Realm schema to another. The schema for a Realm is defined by all classes in a project that extend RealmObject, so any changes to these classes will require a migration. To support migrations from any previous schemaVersion to the newest, the following pattern is recommended when writing a migration:

 public class CustomMigration implements RealmMigration {
   \@Override
   public long execute(Realm realm, long schemaVersion) {
     if (schemaVersion == 0) {
       // Migrate from v0 to v1
       schemaVersion++;
     }

     if (schemaVersion == 0) {
       // Migrate from v0 to v1
       schemaVersion++;
     }

     return schemaVersion;
   }
 }
 

During development when model classes can change frequently, it is possible to use Realm.deleteRealm(RealmConfiguration). This will delete the database file and eliminate the need for any migrations.

See Also:

Realm.migrateRealm(RealmConfiguration), Realm.migrateRealm(RealmConfiguration, RealmMigration)

Method Summary

Modifier and Type	Method and Description
long	execute(Realm realm, long version) Implement this method in your subclass to perform migration.

Method Detail

execute

long execute(Realm realm,
             long version)

Implement this method in your subclass to perform migration.

Parameters:

realm - The Realm on which to perform the migration.

version - The schemaVersion of the Realm at the start of the migration.

Returns:

The schemaVersion of the Realm after executing the migration.