Create a DAO Class

Kotlin and Android Development featuring Jetpack — by Michael Fazio (41 / 125)

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As I mentioned before, we’re not going to be calling the PennyDropDatabase directly to get our data but will instead send everything through a DAO, or data access object. We mark an interface or abstract class as a DAO via the @Dao annotation. Most of the work with PennyDropDao will be handled by the Room library, leaving us to only worry about custom actions as needed. A majority of the functions in the DAO will be abstract with a particular annotation to give the function a purpose. If we need more control over what a function does, we can still write full SQL queries as well. In our case, we only need a single @Query function, with the other functions either using the @Insert or @Update annotations. The PennyDropDao abstract class with a couple of functions looks like this:

​ @Dao
​ ​abstract​ ​class​ PennyDropDao {
​   @Query(​"SELECT * FROM players WHERE playerName = :playerName"​)
​   ​abstract​ ​fun​ ​getPlayer​(playerName: String): Player?
​ 
​   @Insert
​   ​abstract​ ​suspend​ ​fun​ ​insertGame​(game: Game): Long
​ 
​   @Insert
​   ​abstract​ ​suspend​ ​fun​ ​insertPlayer​(player: Player): Long
​ 
​   @Insert
​   ​abstract​ ​suspend​ ​fun​ ​insertPlayers​(players: List<Player>): List<Long>
​ 
​   @Update
​   ​abstract​ ​suspend​ ​fun​ ​updateGame​(game: Game)
​ }