Room: How to use @Transaction in DAO Interface

Question

Regarding this question's answer: How to use setBalance method in my entity to set the actual balance value of a member?

The answer suggests to use a @Transaction method. I don't understand how to use this method. Also, my DAO is an interface, the answer's DAO is a abstract.

How do I implement the method suggested in the answers into my interface DAO and then in the repository?

Answer 1

Transaction methods in room are methods marked with @Transaction annotation.

Since you can not have non-abstract methods in interfaces, you need to use an abstract class instead of interface for DAO.

For example,

@android.arch.persistence.room.Dao
public abstract class AppDao {
    @Transaction
     public void insertAndDeleteInTransaction(Product newProduct, Product oldProduct) {
         // Anything inside this method runs in a single transaction.
         insert(newProduct);
         delete(oldProduct);
     }
}