I have a *ProductDao* interface class which implemented(?) by *ProductDatabase*. Maybe I should not ...

# android

[Aiden]

I have a ProductDao interface class which implemented(?) by ProductDatabase.
Maybe I should not say implemented(?), because it is not using the implements word.

1. Why the ProductDatabase can use abstract to initialize interface class? abstract fun productDao(): ProductDao
2. What does the line of code means and trying to do?

@Database(entities = [Product::class], version = 1)
abstract class ProductDatabase : RoomDatabase() {
    abstract fun productDao(): ProductDao
}

@Dao
interface ProductDao {
    @Insert
    fun insert(product: Product)

    @Update
    fun update(product: Product)

    @Delete
    fun delete(product: Product)

    @Query("SELECT * FROM products")
    fun all(): LiveData<Array<Product>>

    @Query("SELECT * FROM products WHERE id = :id")
    fun get(id: Int): Product
}

[bezrukov]

better to say ProductDatabase provides ProductDao
Room generates ProductDao_Impl that implements ProductDao and ProductDatabase_Impl that implements ProductDatabase for you.

[bezrukov]

And answers:

1. because ProductDatabase_Impl implements this fun
2. In impl it simply creates ProductDao_Impl(db)

[bezrukov]

You can simply review the generated code after assemble:
navigate to mentioned classes by search OR simply click bottom arrow in the left bar near any abstract declaration

[Ayden]

Thank you!!