Looks like in current implementation objects with polymorphic types are serialized as<

Another example in klaxon "Polymorphic classes" <a href="https://github.com/cbeust/kla

JSON: write type inside json-object rather than in array about kotlinx.serialization HOT 5 CLOSED

kotlin commented on August 25, 2024 11

JSON: write type inside json-object rather than in array

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Comments (5)

zvozin commented on August 25, 2024 6

@class should be a configurable field name. E.g. in Jackson:

@JsonTypeInfo(
  use = JsonTypeInfo.Id.NAME, 
  include = JsonTypeInfo.As.PROPERTY, 
  property = "type")
@JsonSubTypes({ 
  @Type(value = Car.class, name = "car"), 
  @Type(value = Truck.class, name = "truck") 
})

This would be highly useful - things that get JSON-serialized are more often than not algebraic data types.

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raderio commented on August 25, 2024 1

Another example in klaxon "Polymorphic classes" https://github.com/cbeust/klaxon#polymorphic-classes

[
    { "type": "rectangle", "width": 100, "height": 50 },
    { "type": "circle", "radius": 20}
]

@TypeFor(field = "type", adapter = ShapeTypeAdapter::class)
open class Shape(val type: String)
data class Rectangle(val width: Int, val height: Int): Shape()
data class Circle(val radius: Int): Shape()

class ShapeTypeAdapter: TypeAdapter<Shape> {
    override fun classFor(type: Any): KClass<out Shape> = when(type as String) {
        "rectangle" -> Rectangle::class
        "circle" -> Circle::class
        else -> throw IllegalArgumentException("Unknown type: $type")
    }
}

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raderio commented on August 25, 2024 1

Any plans for this?

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hastebrot commented on August 25, 2024

Seems KInput needs to be able to peek for values in order to implement a serial loader that can read polymorphic values with @class.

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raderio commented on August 25, 2024

Also, will be very useful to support multi-level inheritance.
An example will be for articles, it can be published or draft, and it can also have types: text, link, video.

[
    { "state": "draft", "type": "link", "url": "http..." },
    { "state": "published", "type": "link", "url": "http..." },
    { "state": "published", "type": "text", "content": "xyz" }
]

from kotlinx.serialization.

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