Update

Marks a method in a Dao annotated class as an update method.

The implementation of the method will update its parameters in the database if they already exists (checked by primary keys). If they don't already exists, this option will not change the database.

All of the parameters of the Update method must either be classes annotated with Entity or collections/array of it.

Example:

@Dao
public interface MusicDao {
    @Update
    fun updateSong(song: Song)

    @Update
    fun updateSongs(songs: List<Song>): Int
}

If the target entity is specified via entity then the parameters can be of arbitrary POJO types that will be interpreted as partial entities. For example:

@Entity
data class Playlist (
    @PrimaryKey(autoGenerate = true)
    val playlistId: Long,
    val name: String,
    @ColumnInfo(defaultValue = "")
    val description: String,
    @ColumnInfo(defaultValue = "normal")
    val category: String,
    @ColumnInfo(defaultValue = "CURRENT_TIMESTAMP")
    val createdTime: String,
    @ColumnInfo(defaultValue = "CURRENT_TIMESTAMP")
    val lastModifiedTime: String
)

data class PlaylistCategory (
  val playlistId: Long,
  val category: String,
  val lastModifiedTime: String
)

@Dao
public interface PlaylistDao {
  @Update(entity = Playlist::class)
  fun updateCategory(varargs category: Category)
}

Summary

Update(
    entity: KClass<*> = Any::class,
    onConflict: Int = OnConflictStrategy.ABORT
)

val entity: KClass<*>

val onConflict: Int