Generic Repository Interface

DataSource.kt

/**
 * Default interface for DAOs.
 */
interface DataSource<T> {

    fun all(): List<T>

    fun readById(id: String): T

    fun insertOrUpdate(item: T)

    fun insertOrUpdate(items: List<T>)

    fun delete(item: T)

    fun deleteAll()

    fun delete(predicate: (T) -> Boolean)
}

Repository.kt

import androidx.lifecycle.LiveData

/**
 * Generic interface for working with [T]
 */
interface Repository<T> {

    /**
     * Gets all [T].
     */
    suspend fun all(): LiveData<List<T>>

    /**
     * Gets [T] by id.
     */
    suspend fun getById(id: String): LiveData<T>

    /**
     * Deletes [T].
     */
    suspend fun delete(item: T)

    /**
     * Deletes [T] by predicate.
     */
    suspend fun delete(predicate: (T) -> Boolean)

    /**
     * Updates and inserts [T].
     */
    suspend fun insertOrUpdate(item: T)

    /**
     * Updates and inserts list of [T].
     */
    suspend fun insertOrUpdate(items: List<T>)
}