Room:在函数体中抓取道选数据，经过额外处理后返回

@Entity(tableName = "user_table")
public class User {
    @PrimaryKey(autoGenerate = true)
    private int id;
    private String name;
    private int age;

    // Getters and Setters
}

@Dao
public interface UserDao {
    @Query("SELECT * FROM user_table")
    LiveData<List<User>> getAllUsers();

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void insert(User user);
}

public class UserRepository {
    private UserDao userDao;
    private LiveData<List<User>> allUsers;

    public UserRepository(Application application) {
        UserDatabase db = UserDatabase.getDatabase(application);
        userDao = db.userDao();
        allUsers = userDao.getAllUsers();
    }

    public LiveData<List<User>> getAllUsers() {
        return allUsers;
    }

    public void insert(User user) {
        new InsertAsyncTask(userDao).execute(user);
    }

    private static class InsertAsyncTask extends AsyncTask<User, Void, Void> {
        private UserDao asyncTaskDao;

        InsertAsyncTask(UserDao dao) {
            asyncTaskDao = dao;
        }

        @Override
        protected Void doInBackground(final User... params) {
            asyncTaskDao.insert(params[0]);
            return null;
        }
    }
}

class UserRepository(private val userDao: UserDao) {
    val allUsers: LiveData<List<User>> = userDao.getAllUsers()

    suspend fun insert(user: User) {
        withContext(Dispatchers.IO) {
            userDao.insert(user)
        }
    }

    fun processAndReturnUsers(): LiveData<List<ProcessedUser>> {
        return Transformations.map(allUsers) { users ->
            users.map { user ->
                // 进行额外的数据处理
                ProcessedUser(user.name.toUpperCase(), user.age + 1)
            }
        }
    }
}