Use Dao inheritance to reduce the amount of boilerplate code - https://medium.com/google-developers/7-pro-tips-for-room-fbadea4bfbd1

README.md

Use Dao inheritance to reduce the amount of boilerplate code

For details check out 7 Pro-tips for Room!

BaseDao.kt

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.db

import android.arch.persistence.room.Delete
import android.arch.persistence.room.Insert
import android.arch.persistence.room.Update

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)
}

Data.kt

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.db

import android.arch.persistence.room.Entity
import android.arch.persistence.room.PrimaryKey

@Entity(tableName = "data")
data class Data(@PrimaryKey val id: String, val value: String)

DataDao.kt

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.db

import android.arch.persistence.room.Dao
import android.arch.persistence.room.Query

@Dao
abstract class DataDao : BaseDao<Data>() {

    /**
     * Get all data from the Data table.
     */
    @Query("SELECT * FROM Data")
    abstract fun getData(): List<Data>
}

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User.kt

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.db

import android.arch.persistence.room.Entity
import android.arch.persistence.room.PrimaryKey
import java.util.*

@Entity
data class User(@PrimaryKey
                val id: String,
                val userName: String)

UserDao.kt

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.db

import android.arch.lifecycle.LiveData
import android.arch.persistence.room.Dao
import android.arch.persistence.room.Query
import io.reactivex.Flowable

/**
 * Data Access Object for the users table.
 */
@Dao
abstract class UserDao : BaseDao<User>() {

    /**
     * Get a user by id.

     * @return the user from the table with a specific id.
     */
    @Query("SELECT * FROM USER WHERE id = :id")
    abstract fun getUserById(id: String): Flowable<User>

    /**
     * Delete all users.
     */
    @Query("DELETE FROM USER")
    abstract fun deleteAllUsers()
}

I'm trying to implement this in my project, but I'm getting this error
An abstract DAO method must be annotated with one and only one of the following annotations: Insert,Delete,Query,Update,RawQuery

@lostlegacy I've got the same issue regarding fun getById(id: D): T
In my case a temporary workaround is a method:

@JvmSuppressWildcards
fun findAll(ids: Collection<D>): List<T>

Hi @florina-muntenescu, thank you for this gist. I just wondering if I can do something like this 👍

interface BaseDao<T,D> {
   
    @Insert
    fun insert(vararg obj: T)

    @Update
    fun update(obj: T)

    @Delete
    fun delete(obj: T)

// I want to add these methods as default implementation for all of my DAO classes
    fun getById(id: D): T
    
    fun deleteById(id: D)
}

with those method will be overrided by its subclasses like this:

interface FooDao : BaseDao<Foo,Int>{
    @Query(SELECT * FROM foo WHERE id = :id)
    fun getById(id: Int): Foo
   
    @Query(DELETE FROM foo WHERE id = :id)
    fun deleteById(id: Int)
}

I'm trying to implement this in my project, but I'm getting this error
An abstract DAO method must be annotated with one and only one of the following annotations: Insert,Delete,Query,Update,RawQuery

Does it help if you add the override modifier to those methods in FooDao?

it starts to cause problems when i define some function in the DAO with @trasaction anotation as it is not allowed to use more than one annotation ,
ERROR LOG: error: An abstract DAO method must be annotated with one and only one of the following annotations: Insert,Delete,Query,Update,RawQuery

Hi @florina-muntenescu, thank you for this gist. I just wondering if I can do something like this +1

interface BaseDao<T,D> {
   
    @Insert
    fun insert(vararg obj: T)

    @Update
    fun update(obj: T)

    @Delete
    fun delete(obj: T)

// I want to add these methods as default implementation for all of my DAO classes
    fun getById(id: D): T
    
    fun deleteById(id: D)
}

with those method will be overrided by its subclasses like this:

interface FooDao : BaseDao<Foo,Int>{
    @Query(SELECT * FROM foo WHERE id = :id)
    fun getById(id: Int): Foo
   
    @Query(DELETE FROM foo WHERE id = :id)
    fun deleteById(id: Int)
}

I'm trying to implement this in my project, but I'm getting this error
An abstract DAO method must be annotated with one and only one of the following annotations: Insert,Delete,Query,Update,RawQuery

Does it help if you add the override modifier to those methods in FooDao?

Were you able to get this to work?

I am trying to do something similar:

package com.goodyear.rtms.database

import androidx.room.Insert
import androidx.room.Update

interface DaoBase<TEntity, TId> where TEntity : Entity<TId> {

    @Insert
    fun add(entity: TEntity)

    fun get(id: TId): TEntity?

    @Update
    fun update(entity: TEntity)
}

fun <TEntity, TId> DaoBase<TEntity, TId>.addOrUpdate(entity: TEntity) where TEntity : Entity<TId> {
    val entityQ = get(entity.id)
    if(entityQ == null) {
        add(entity)
    } else {
        update(entity)
    }
}

with coroutines & insert or update extensions function

interface BaseDao<T> {

    /**
     * Insert an object in the database.
     *
     * @param obj the object to be inserted.
     */
    @Insert(onConflict = OnConflictStrategy.IGNORE)
    suspend fun insert(obj: T): Long

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

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

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

}

@Transaction
suspend inline fun <reified T> BaseDao<T>.insertOrUpdate(item: T) {
    if (insert(item) != -1L) return
    update(item)
}

What if you want to change conflict strategy on insert

Type of the parameter must be a class annotated with @entity or a collection/array of it.

I found it please check your Dao but not BaseDao

ex:  abstract class TalkConnectDao : BaseDao<TalkConnectDao> 
BaseDao<TalkConnectDao> TalkConnectDao is wrong so change  TalkConnectDao  to  TalkConnectEntity

it will ok

   def room_version = "2.2.5"  
   'roomRuntime'                  : "androidx.room:room-runtime:$room_version",
        'roomKtx'                      : "androidx.room:room-ktx:$room_version"

Thanks for sharing that information. keep it up.

I wrote this code for creating any SQL query. in this case, your model name and table name must have the same name

inline fun <reified T> createQuery(): String = return "SELECT * FROM ${getClassName<T>()}"

inline fun <reified T> getClassName() = T::class.java.simpleName

@JvmSuppressWildcards

Me too

Awesome！

Awesome !Thank's very much