Hi Everyone ! Let's say I have a class that extends List class , and I am using it as a property in ...

# serialization

[Waqas Tahir]

Hi Everyone !
Let's say I have a class that extends List class , and I am using it as a property in another class that I want to serialize , How can I write serializer , I just want to cast that property to a List and then serialize and deserialize as a List , does anyone reply here ?

[Ben Woodworth]

Take a look at this:
https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/serializers.md#composite-serializer-via-surrogate

[Waqas Tahir]

class SnapshotListSerializer<T>(private val dataSerializer: KSerializer<T>) :
    KSerializer<SnapshotStateList<T>> {

    override val descriptor: SerialDescriptor = ListSerializer(dataSerializer).descriptor

    override fun serialize(encoder: Encoder, value: SnapshotStateList<T>) {
        val list = value as List<T>
        encoder.encodeSerializableValue(ListSerializer(dataSerializer), list)
    }

    override fun deserialize(decoder: Decoder): SnapshotStateList<T> {
        val list = mutableStateListOf<T>()
        val items = decoder.decodeSerializableValue(ListSerializer(dataSerializer))
        list.addAll(items)
        return list
    }
}

I've written this serializer , that I can specify , do you think it should work ?

[Ben Woodworth]

Yeah that looks good to me! In serialize you probably don't even need to make a separate List variable, just pass value directly

[Waqas Tahir]

error: incompatible types: Class<SnapshotListSerializer> cannot be converted to Class<? extends KSerializer<?>>
@kotlinx.serialization.Serializable(utils.serializers.SnapshotListSerializer.class)

[Waqas Tahir]

Used it like this

@Serializable(with = SnapshotListSerializer::class)
val items = mutableStateListOf<ListItem>()

[Ben Woodworth]

Does mutableStateListOf() return a subtype of SnapshotStateList? Because you'll have to write a serializer specifically for MutableStateList.
(Your serializer only creates a SnapshotStateList, so kotlinx.serialization doesn't know how to turn it into a mutable one)

[Waqas Tahir]

mutableStateListOf returns SnapshotStateList , I am getting this everywhere where I specified a serializer as a parameter in the annotation , think some kind of bug or something , let me know if you know about it , Thanks for the help though !!

[Ben Woodworth]

If SnapshotStateList is an interface then that might be the problem (@Serializable doesn't work on interfaces). But that's the only thing I can think of... glad I could help!