Tutorial 5

Save useful data locally.

Use DataStore for small preferences and Room for structured app data. Do not force everything into one storage mechanism.

Storage choice

DataStore	Theme, language, onboarding seen, selected city, sort preference.
Room	Favourite businesses, cached catalogue rows, notes, records with ids.
Network only	Fresh data that can be re-fetched and does not need offline use.

Room-style favourite entity

@Entity(tableName = "favourites")
data class FavouriteBusinessEntity(
    @PrimaryKey val businessId: Int,
    val savedAtMillis: Long
)

@Dao
interface FavouriteBusinessDao {
    @Query("SELECT * FROM favourites")
    suspend fun getAll(): List<FavouriteBusinessEntity>

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun save(entity: FavouriteBusinessEntity)

    @Query("DELETE FROM favourites WHERE businessId = :id")
    suspend fun remove(id: Int)
}

Practice task

Save selected city or language using DataStore.
Save favourite business ids using Room or a simple local abstraction first.
Show favourites after app restart.
Write down why each value belongs in its chosen storage.

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