@Target(allowedTargets = [AnnotationTarget.FUNCTION])
@Retention(value = AnnotationRetention.BINARY)
public annotation Update

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

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

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

Example:

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

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

If a target entity is specified via entity value then the parameters can be of arbitrary data object 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
interface PlaylistDao {
    @Update(entity = Playlist::class)
    suspend fun updateCategory(varargs category: Category)
}
See also
Delete
Insert
Upsert

Summary

Public constructors
Update(@NonNull KClass<@NonNull ?> entity, int onConflict)

Public methods
final @NonNull KClass<@NonNull ?>

The target entity of the update function.
final int

What to do if a conflict happens.

Public constructors

Update

Added in 3.0.0-alpha01
public Update(@NonNull KClass<@NonNull ?> entity, int onConflict)

Public methods

getEntity

public final @NonNull KClass<@NonNull ?> getEntity()

The target entity of the update function.

When this is declared, the update function parameters are interpreted as partial entities when the type of the parameter differs from the target. The data object class that represents the entity must contain a subset of the properties of the target entity along with its primary keys.

Only the columns represented by the partial entity properties will be updated if an entity with equal primary key is found.

By default, the target entity is interpreted by the function parameters.

Returns
@NonNull KClass<@NonNull ?>

the target entity of the update function or none if the function should use the parameter type entities.

getOnConflict

@OnConflictStrategy
public final int getOnConflict()

What to do if a conflict happens.

Use OnConflictStrategy.ABORT (default) to roll back the transaction on conflict. Use OnConflictStrategy.REPLACE to replace the existing rows with the new rows. Use OnConflictStrategy.IGNORE to keep the existing rows.

Returns
int

How to handle conflicts. Defaults to OnConflictStrategy.ABORT.