Android Room @TypeConverter using Kotlin

AppDatabse.kt

@Database(entities = arrayOf(Note::class, User::class), version = 1)
@TypeConverters(Converters::class)
abstract class AppDatabse : RoomDatabase() {

    abstract fun userDAO(): UserDAO
    abstract fun noteDAO(): NoteDAO

}

Converters.kt

package com.tinmegali.daggerwithkotlin.room

import android.arch.persistence.room.TypeConverter

import java.util.Date


class Converters {

    @TypeConverter
    fun fromTimestamp(value: Long?): Date? {
        return if (value == null) null else Date(value)
    }

    @TypeConverter
    fun dateToTimestamp(date: Date?): Long? {
        return date?.time
    }

}

thank you a lot

thank you

Thank you!

Awesome example.
Thanks! 👍

It's better to declare Converters as a singleton in order not to create any extra objects. You shoud also mark all inner converter functions with @JvmStatic so Room can use them as regular static functions

@NikolayKul like this?

class RoomConverters {

    companion object {
        @TypeConverter @JvmStatic
        fun meToString(me: MyEnum): String = ds.name

        @TypeConverter @JvmStatic
        fun sToMyEnum(s: String): MyEnum = MyEnum.valueOf(s)

        //Add more converters here, or make another class altogether
    }

}

@louistsaitszho it's more along the lines of this:

object RoomConverters {

    @TypeConverter
    @JvmStatic
    fun meToString(me: MyEnum?) = ds?.name

    @TypeConverter
    @JvmStatic
    fun sToMyEnum(s: String?) = s?.let(MyEnum::valueOf)

    // Add more converters here, or make another class altogether
}

@aouerfelli oh yea I can just skip the class. But I got 1 more question: what if it is not nullable? And what if both nullable and non-nullable exists? How should I handle Entity like this:

@Entity
data class ToBePush(
    @PrimaryKey val id: Int,
    val value: Int.
    val createDate: Date,
    val syncDate: Date? = null
)

Should I create more @TypeConverter functions for both Date and Date?, or should I just have one set for Date??

@louistsaitszho it's better to have them nullable to handle all use cases.

Awesome! Thanks.

How should we use the RoomConverters object?
here it is:
https://developer.android.com/training/data-storage/room/referencing-data

please note that @aouerfelli approach will not work if you need to use object members (for example instance of moshi)

please note that @aouerfelli approach will not work if you need to use object members (for example instance of moshi)

Please go into detail.

How should we use the RoomConverters object?
here it is:
https://developer.android.com/training/data-storage/room/referencing-data

@marco-silva0000 really appricate that. All of the examples I see on the internet never reference the official docs.

Converter ArrayList to String (gson) / String (gson) to ArrayList

class ListStringConverter {

@TypeConverter
fun fromString(value: String): List<String> {
    val listType = object : TypeToken<List<String>>() {}.type
    return Gson().fromJson(value, listType)  

}

@TypeConverter
fun fromListLisr(list: List<String>): String {
    val gson = Gson()
    return gson.toJson(list)
}

}

Converter ArrayList to String (gson) / String (gson) to ArrayList

class ListStringConverter {

@TypeConverter
fun fromString(value: String): List<String> {
    val listType = object : TypeToken<List<String>>() {}.type
    return Gson().fromJson(value, listType)  

}

@TypeConverter
fun fromListLisr(list: List<String>): String {
    val gson = Gson()
    return gson.toJson(list)
}

}

Wouldn't be easier to do just:

class Converters {
    @TypeConverter
    fun toListOfStrings(flatStringList: String): List<String> {
        return flatStringList.split(",")
    }
    @TypeConverter
    fun fromListOfStrings(listOfString: List<String>): String {
        return listOfString.joinToString(",")
    }
}

Is there any way to Convert a single column of a table but in the same Type? Like from String to String?

How can i do it here if data is ProfileDataResponceModel

Main Profile class
@Entity(tableName = "profile_list")
data class ProfileResponseModel(
@Embedded(prefix = "profile_")
val data: ProfileDataResponseModel,
val status: Int,
val message: String
)
ProfileData

data class ProfileDataResponseModel(
val uid: Int?,
val name: String?,
val surname: String?,
val position: String?,
val department: String?,
val phone: String?,
val email: String?,
val contacts: String?,
val home: String?,
val password: String?
)

How do I create a converter of my own Object. Let us say I have an User object and I want to add this entity to the database

@entity
data class Users(val orderId: UUID, val orderDate: Date, val manager: Manager, val office: Office) {}

I have the Manager class and the Office class that I want to us a converter, how do I go about that?

Thanks

to use*

For some reason converting kotlin.time.Duration does not work but java.time.Duration

Are there a generic Converter for enum? Or do we need write specific converter for each enum that used?