Android Room Generic DAO

Good day Stack, i'm working on an Android project that uses Android's Room 1.0.0 Alpha 5, the main issue that i'm facing is that every time i need to call one of the DAO from room

Solution 1:

You can use inheritance and create a BaseDao which will be implemented by all your child Dao. This way you won't need to write the common methods again and again.

interface BaseDao<T> {

/**
 * Insert an object in the database.
 *
 * @param obj the object to be inserted.
 */
@Insert
fun insert(obj: T)

/**
 * Insert an array of objects in the database.
 *
 * @param obj the objects to be inserted.
 */
@Insert
fun insert(vararg obj: T)

/**
 * Update an object from the database.
 *
 * @param obj the object to be updated
 */
@Update
fun update(obj: T)

/**
 * Delete an object from the database
 *
 * @param obj the object to be deleted
 */
@Delete
fun delete(obj: T)
}

Read more about it: https://gist.github.com/florina-muntenescu/1c78858f286d196d545c038a71a3e864#file-basedao-kt

Original credits to Florina.

Solution 2:

I played around a bit with the answer of Akshay Chordiya, but needed two additions:

• ability to insert/update List
• return values to monitor insert/update success

Here is what I came up with:

import androidx.room.Dao
import androidx.room.Insert
import androidx.room.OnConflictStrategy
import androidx.room.Update

/**
 * List of all generic DB actions
 * All use suspend to force kotlin coroutine usage, remove if not required
 */
@Dao
interface BaseDao<T> {

    // insert single
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insert(obj: T?): Long

    // insert List
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insert(obj: List<T>?) : List<Long>

    // update List
    @Update
    suspend fun update(obj: List<T>?): Int

}

---

@Dao
interface MyObjectDao : BaseDao<MyObject> {

    @Query("SELECT * from $TABLE_NAME WHERE $COL_ID = :id")
    suspend fun getById(id: Long): MyObject

}

---

Can then be called like:

val ids = MyObjectDao.insert(objectList)