I used to use Realm and I am currently testing Room in order to compare both tools.
I am trying to implement the following many to many relation :
Here my Entity classes :
The Person :
@Entity(tableName = "person")
public final class RoomPerson {
@PrimaryKey
public int id;
public String name;
}
The Cat class :
@Entity(tableName = "cat")
public final class RoomCat {
@PrimaryKey
public int id;
public int age;
public String name;
}
And the PersonCat class :
@Entity(tableName = "person_cat", primaryKeys = { "personId", "catId" },
indices = { @Index(value = { "catId" }) },
foreignKeys = { @ForeignKey(entity = RoomPerson.class, parentColumns = "id", childColumns = "personId"),
@ForeignKey(entity = RoomCat.class, parentColumns = "id", childColumns = "catId") })
public final class RoomPersonCat {
public int personId;
public int catId;
public RoomPersonCat(int personId, int catId) {
this.personId = personId;
this.catId = catId;
}
}
I also have a POJO in order to manipulate a person with cats into my app :
public final class RoomPersonWithAnimals {
@Embedded
public RoomPerson person;
@Relation(parentColumn = "id", entityColumn = "id", entity = RoomCat.class)
public List<RoomCat> cats;
}
The question is : how to save a List<RoomPersonWithAnimals> ?
Should I do 3 requests each time in order to save :
- the person into the table
Person - the cats into the table
Cat - its cats into the table
PersonCat
Here the java code that illustrate the 3 requests :
for (RoomPersonWithAnimals personWithAnimals : persons) {
myRoomDatabase.roomPersonDao().insert(personWithAnimals.person);
myRoomDatabase.roomCatDao().insertAll(personWithAnimals.cats.toArray(new RoomCat[personWithAnimals.cats.size()]));
for (RoomCat cat : personWithAnimals.cats) {
myRoomDatabase.roomPersonCatDao().insert(new RoomPersonCat(personWithAnimals.person.id, cat.id));
}
}
In Realm, it's possible to save in only one request these data. Is is a limitation of Room or my implementation is wrong ?
Thank you in advance for your help !
