Hi, is there a way to provide a fallback/default deserializer when `JsonClassDiscriminator` is not f...

# serialization

[Bao Le Duc]

Hi, is there a way to provide a fallback/default deserializer when JsonClassDiscriminator is not found?
Background: I have a data class

@Serializable
@JsonClassDiscriminator("type")
sealed interface Messaging {
    @Serializable
    @SerialName("inc_messaging_usermsg")
    data class UserMsg(
        val content: String
    ) : Messaging

    @Serializable
    @SerialName("inc_messaging_youfollow")
    data class YouFollow(
        val name: String
    ) : Messaging

    @Serializable
    @SerialName("inc_messaging_usermsgwdata")
    data class UsermsgWithData(
        val attachment: MessagingAttachment
    ) : Messaging
    
    /**
     * object Default : Messaging
     */
}

As we may add new type of messages in the future, I would add object Default : Messaging as a fallback option if new type is introduced

[Dominaezzz]

Yes, you can specify it when creating the JSON serial format

[Bao Le Duc]

Could you give a bit more details? I got an exception likes

kotlinx.serialization.json.internal.JsonDecodingException: Polymorphic serializer was not found for class discriminator 'some unknown type'

[Dominaezzz]

Ah no I misread the problem

[Dominaezzz]

You can specify a default serialiser in the serialiser module

[Dominaezzz]

I'm on my phone so I can't write you an example

[Bao Le Duc]

found it

polymorphicDefaultDeserializer(MessagingPayload::class) {
                UnkownMessagingPayload.serializer()
            }

Thanks for the tips @Dominaezzz

[Jorge Rodríguez]

I think that is more accurate if you use abstract classes instead of sealed classes. What you need to be worry is that your json contains the type discriminator.