MVVM on Android
Notes: 04. Model the Repository
The version of the architecture components to add is 2.5.0. Check the download materials for the updated ViewModel and LiveData dependencies.
suspend should be added to the saveCreature and clearAllCreatures methods definition in the CreatureRepository interface.
So the interface should look like this:
interface CreatureRepository {
suspend fun saveCreature(creature: Creature)
fun getAllCreatures(): LiveData<List<Creature>>
suspend fun clearAllCreatures()
}
The RoomRepository class no longer uses AsyncTask. Instead it used Kotlin Coroutines.
Check the download materials for the updated code or take a look at what it looks like below:
class RoomRepository : CreatureRepository {
private val creatureDao: CreatureDao = CreaturemonApplication.database.creatureDao()
private val allCreatures: LiveData<List<Creature>>
init {
allCreatures = creatureDao.getAllCreatures()
}
override suspend fun saveCreature(creature: Creature) {
creatureDao.insert(creature)
}
override fun getAllCreatures() = allCreatures
override suspend fun clearAllCreatures() {
val creatureArray = allCreatures.value?.toTypedArray()
if (creatureArray != null) {
creatureDao.clearCreatures(*creatureArray)
}
}
}
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In this video, we’re going to setup a Repository in which we’ll save our Model data. Our concrete repository is going to be a Room database, and we’re going to use LiveData from the Android Architecture Components library to retrieve data from the database.
arch_comp_version = '1.1.1'
// ViewModel and LiveData
implementation "android.arch.lifecycle:extensions:$arch_comp_version"
interface CreatureRepository {
fun saveCreature(creature: Creature)
fun getAllCreatures(): LiveData<List<Creature>>
fun clearAllCreatures()
}
@Entity(tableName = "creature_table")
data class Creature(
val attributes: CreatureAttributes = CreatureAttributes(),
val hitPoints: Int = 0,
@PrimaryKey @NonNull val name: String,
val drawable: Int = 0
)
interface CreatureDao {
@Insert(onConflict = OnConflictStrategy.REPLACE)
fun insert(creature: Creature)
@Delete
fun clearCreatures(vararg creature: Creature)
@Query("SELECT * FROM creature_table ORDER BY name ASC")
fun getAllCreatures(): LiveData<List<Creature>>
}
@TypeConverters(CreatureAttributesConverter::class)
private val allCreatures: LiveData<List<Creature>>
init {
allCreatures = creatureDao.getAllCreatures()
}
override fun saveCreature(creature: Creature) {
InsertAsyncTask(creatureDao).execute(creature)
}
override fun getAllCreatures() = allCreatures
override fun clearAllCreatures() {
val creatureArray = allCreatures.value?.toTypedArray()
if (creatureArray != null) {
DeleteAsyncTask(creatureDao).execute(*creatureArray)
}
}
dao.clearCreatures(*params)
database = Room.databaseBuilder(this, CreatureDatabase::class.java, "creature_database")
.build()