I m trying to find a way of dealing with GeoJson <https tool kotlinlang #serialization

I’m trying to find a way of dealing with GeoJson (https://tools.ietf.org/html/rfc7946) in a multiplatform way. The specification indicates that the type of the property

coordinates

depends on the first property

type

. Expamples:

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{
  "type": "Point",
  "coordinates": [
    100,
    0
  ]
}

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{
  "type": "LineString",
  "coordinates": [
    [
      100,
      0
    ],
    [
      101,
      1
    ]
  ]
}

sandwwraith

02/05/2018, 10:31 PM

Unfortunately, current implementation can’t make decisions how to deserialize object depending on a field inside the object

gaetan

02/06/2018, 8:47 AM

Thanks for the answer.

gildor

02/08/2018, 12:28 AM

Oh, this format is really bad :(

Maybe somehow possible to deserialize to array of dynamics, or to your own class with custom deserializer (kotlinx.serialization support that, as I understand), because I just do not understand how you can map such structure to class, maybe only to some generic Json structure

I mean this problem is not specific for Kotlin serialization, but for any mapping

gaetan

02/08/2018, 8:32 AM

I agree with you about the format but it’s a specification so it should be a use case taked in account. It’s possible with jackson: https://github.com/opendatalab-de/geojson-jackson.

gildor

02/08/2018, 8:35 AM

Using JsonSubTypes?

It’s still custom parsing, but with help of Jackson

my point that you probably should to write custom adapter for kotlinx.serialization, that handled this case.

gaetan

02/08/2018, 8:38 AM

I don’t know if kotlinx.serialization is still a help for the moment. I think i have to do all the work by custom code and then copy data into some data class.

gildor

02/08/2018, 8:38 AM

Not sure that this is possible for abstract classes how for Jackson (probably make sense to ask about such feature), but at least you can have custom non-abstract wrapper above GeoJsonObject

Yes, but you can write custom serializer, so you can copy data to any data class https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/custom_serializers.md

gaetan

02/08/2018, 8:44 AM

Maybe I should do it in two times: a first object that is used only for the

type

field. Then, when I know the type, I can use the right specialized class.

gildor

02/08/2018, 9:01 AM

Not sure, but I think using custom serilizers you can even read type and then deserialize only “coordinates” content separately

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