Argthtjtr

I'm starting to pick up Kotlin since a few days.
Atm I am trying to write an abstract Dao class with common functions (copyOrUpdate, delete, ...), but I'm stuck on findFirst & findAll.
My database is Realm.

This is a piece of my Dao:

    abstract class Dao<T : RealmModel>() {



    //Get Realm Instance

    val db: Realm by lazy {

        Realm.getDefaultInstance()

    }



    //Delete - 1 Object

    fun delete(input: T) {



        if (db.isInTransaction) {

            input.deleteFromRealm()

        } else {

            db.executeTransaction { realm -> input.deleteFromRealm() }

        }

    }

}

I am struggling to add a findFirst() function. I'm not sure if this is possible. Here is a non-working piece of struggle:

//Get First

fun findFirst(classType: T): T {



    return db.where(T::class.java)

        .findFirst()

}

Is there any way to solve this?
At the moment this function is in my UserDao class.

class UserDao() : Dao<User>() {    

   //where

    private fun where(): RealmQuery<User> {

        return db.where<User>()

    }



    // Find First

    fun findFirst(): User? {

        return where()

            .findFirst()

    }

}

I would go with extension + inline fun

inline fun <reified T : RealmModel> Realm.findFirst(): T? {

    return where(T::class.java).findFirst()

}

Pass Class<T> into the constructor:

abstract class Dao<T : RealmModel>(private val cls: Class<T>) {    

    fun findFirst(): T? {

        return db.where(cls).findFirst()

    }

}



class UserDao() : Dao<User>(User::class.java) { ... }

Kotlin's reified type parameters allow you to avoid or hide it in some circumstances, but not with abstract classes.