Room - check if data were fetched recently

Question

In official Guide to App Architecture is an exaple of repository. There is a check if an object is existing in database and if is fresh:

// check if user was fetched recently
boolean userExists = userDao.hasUser(FRESH_TIMEOUT);

Any ideas how to implement that functionality (hasUser) for DAO?

Answer 1

Most Architecture Components examples are available here. In your case, I couldn't find the UserDao class but there is a database schema sample here. users table has a last_update column. So you could write UserDao like this :

@Query("SELECT COUNT(*) FROM users WHERE userId == :userId AND last_update >= :timeout)
int hasUser(int userId, long timeout)

It returns 0 if the user with id userId is not fresh enough.