kotlinlang #serialization

with mutable and nullable representation for automatic Firestore serialization. I added companion functions to convert between the two, and that deals with specific differences (e.g. date representations). It means some extra code, but it also means that Firebase limitations don’t propagate through my codebase and I get to be explicit about the conversion. That’s the solution I ended up with, although I’d be curious if other good patterns have emerged.

Gilles Barbier

05/16/2021, 8:54 PM

Hello, can serialization 1.2+ be used with kotlin 1.4+ ?

Daniele B

05/17/2021, 8:38 AM

instead of Json format:

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val obj = Json.decodeFromString<Data>("""{"a":42, "b": "str"}""")

is there a way to decode key/value pairs concatenated by

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a=42&b=str

or should I convert my key/value pairs into Json?

Daniele B

05/17/2021, 12:05 PM

Is there any way/trick to enforce that classes implementing a specific interface should always be annotated as

@Serializable

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interface ScreenParams

@Serializable
data class CountriesListParams(val listType: CountriesListType) : ScreenParams

@Serializable
data class CountryDetailParams(val countryName: String) : ScreenParams

all these 3 definitions are on different files, so it can happen to forget to set

@Serializable

If the annotation is forgotten, the app would crash at runtime when visiting that specific screen.

ribesg

05/18/2021, 9:58 AM

I’m still blocked by this using kotlinx.serialization 1.2.1

huehnerlady

05/18/2021, 2:32 PM

Hi, I currently try to generate a json schema from kotlin classes and generating kotlin classes from json schema. For my first part - creating schema from kotlin classes, I ran into this post on stack overflow and there I was pointed to kotlinx.serialization at a very early stage (see here). unfortunately this folder was completely removed in this commit. Now I cannot find any hint of similar classes or how I could achieve just that. Is this still possible with kotlinx.serialization? If so — how? If not — any other idea how I can achieve that?

Dariusz Kuc

05/20/2021, 4:00 AM

Hello 👋 How can we define optional nullable fields so we can distinguish following cases during serialization 1) omitted value 2) explicit

null

3) value set I used a sealed class and custom Jackson deserializer in the past (link) but now I'm looking into serialization and need to support

kotlinx-serialization

. I tried something using custom serializer and "skipping" the encode part when I process an instance of

Undefined

sealed class but that produces me a broken JSON, e.g. given

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data class Wrapper(val name: OptionalInput<String>)

I end up with

{ "name": }

. Any ideas? I don't see any option to skip element in the

JsonEncoder

Denys

05/20/2021, 6:05 PM

Help me please. I am trying to update kotlin to version “1.5.0” and kotlinx-serialization-json to version “1.2.0" . After the update, the project stopped building - “java.util.NoSuchElementException: Collection contains no element matching the predicate. at org.jetbrains.kotlinx.serialization.compiler.backend.ir.IrBuilderExtension$DefaultImpls.serializableSyntheticConstructor(GeneratorHelpers.kt:1255)”

Ivan Đorđević

05/21/2021, 8:36 AM

Are serial descriptors generated by the compiler plugin mutable?

natario1

05/21/2021, 5:01 PM

Trying to transform a

class Sms(val phone: String, val code: String)

into

{"sms":{"phone":"1230129","code":"23984"}}

... I know that I can add

SmsWrapper(val sms: Sms)

and require people to use it, but I'd like to use a custom serializer instead. Is there any example to do such thing? I see many examples where structures are flattened (e.g. you remove a

{}

container), but couldn't find one where you do the opposite (nest data in a new

{}

marzelwidmer

05/24/2021, 12:26 PM

Hello have somebody any elegant solution vor validation I saw the following

feature

is still open 🙂 https://github.com/Kotlin/kotlinx.serialization/issues/318 for https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/basic-serialization.md#data-validation

Sam

05/25/2021, 10:43 AM

Hello, good evening everyone. I have a plan replace Gson to Serialization. But My project has many modules, they are using Moshi and Gson in Core module ( base module for all of Features) So What are the pros and cons of using Serialization library? Is there anything I need to keep in mind when switching from Gson to Serialization? Thanks.

zeugederunity

05/25/2021, 12:47 PM

Hello everyone, after upgrading to Kotlin 1.5.10 with kotlinx-serialization-Version 1.2.0 (from Kotlin 1.4.30 and kotlinx-serialization 1.0.1) my code throws the following error:

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java.lang.IllegalStateException: Class Instant have constructor parameters which are not properties and therefore it is not serializable automatically
	at org.jetbrains.kotlinx.serialization.compiler.backend.common.SerializerCodegen.checkSerializability(SerializerCodegen.kt:28)
	at org.jetbrains.kotlinx.serialization.compiler.backend.common.SerializerCodegen.generateSerializableClassPropertyIfNeeded(SerializerCodegen.kt:101)
	at org.jetbrains.kotlinx.serialization.compiler.backend.common.SerializerCodegen.generate(SerializerCodegen.kt:34)

I allready created a minimal Example at: https://github.com/FelixEngl/FailingInstantSerialisation Does anyone know how to fix this?

ushort

05/25/2021, 5:51 PM

Hello, was wondering if anyone can help me understand how a custom decoder should handle maps? Specifically how it might be handled inside decodeElementIndex. I'm having trouble with writing decoder that handles map<string, object>. What currently happens is it decodes one of the map keys, then it switches to class structure and after decoding the class members, it continues to decode the class members of the other key instead of ending the structure and restarting?

tseisel

05/27/2021, 6:35 PM

I need to deserialize 2 versions of an entity

Entity

: one with all properties, and another

SimpleEntity

with only the most used properties from

Entity

. How can I do that? I thought of using closed polymorphism but I can't use a discriminator because I don't control the input JSON.

Goth

05/28/2021, 1:41 AM

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1. this should deserilize to Message<SimmplePayload>
{ 
  id = "1",
  type = "simple",
  payload =  {
    name = "Blah"
  }
}


2. this should deserilize to Message<AdvancedPayload>
{ 
  id = "2",
  type = "advanced",
  payload =  {
    name = "WOW",
    description = "WOW WOW"
  }
}

LastExceed

05/29/2021, 7:04 PM

this jb blog post says

The default serializer is based on an ISO 8601 string representation of a type and uses `toString()`/`parse()` to serialize and deserialize values

the linked wikipedia article lists

2021-05-29T17:42:42+00:00

as an example string so why do i get an exception here ?

-.cpp

Julián Falcionelli

05/30/2021, 11:08 AM

Hi guys, I am facing a serialization issue when using Kotlinx serialization with a Firebase Library in a KMM project. I have the following hierarchy classes that I want to persist in Firebase Realtime Databases.

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@Serializable
sealed class Activity {
  abstract val type: Type

  @Serializable
  enum class Type(
    val enabled: Boolean,
    @Transient
    val shortName: StringResource
  ) {
    BJJ(
      true,
      MR.strings.activity_bjj,
    ),
    GRAPPLING(
      true,
      MR.strings.activity_grappling,
    )
  }

  @Serializable
  data class Bjj(
    override val type: Type = Type.BJJ,
    var belt: Belt? = null,
    val stripes: Int = 0
  ) : Activity() {
    @Serializable
    enum class Belt(
      @Transient
      val color: ColorResource.Single
    ) {
      WHITE(MR.colors.belt_white),
      BLUE(MR.colors.belt_blue),
      PURPLE(MR.colors.belt_purple),
      BROWN(MR.colors.belt_brown),
      BLACK(MR.colors.belt_black)
    }
  }

  @Serializable
  data class Grappling(
    override val type: Type = Type.GRAPPLING
  ) : Activity()
}

I actually send it as a List, something like this: // Firebase Call

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val ref = database
  .child(ROOT_PATH)
  .child(user.id)
  .child("activities")
ref.setValue(ListSerializer(Activity.serializer()), updatedActivities)

Seems that the Firebase Library doesn’t support auto-serialization of sealed classes and I am not sure how to solve this problem.

java.lang.ClassCastException: kotlinx.serialization.descriptors.PolymorphicKind$SEALED cannot be cast to kotlinx.serialization.descriptors.StructureKind

at dev.gitlive.firebase._encodersKt.structureEncoder(_encoders.kt:12)

Spikey Sanju

06/02/2021, 8:30 AM

Hello all, I’m getting error when I try deserialize an object from JSON using Kotlin Serialization. I get the following error 👇

Spikey Sanju

06/03/2021, 10:17 AM

Hello all, Kotlin Serialization works fine for

small chunk of JSON data

. But when I try to

deserialize

the

large JSON file

. It’s throwing me this weird issue. Why is it happening? P.S - I

validated the JSON

. And there’s no issue with it ✅

Kotlin Serialization Issue.mov

pniederw

06/06/2021, 3:48 PM

Is or will it be possible to write a serializer for

Map<String, (Number|Boolean|String)?>

, ideally in a serialization format agnostic way? I guess what I'm asking for is

Decoder.peekType()

. I've looked at

JsonDecoder.decodeJsonElement()

but the implementation is all

internal

LastExceed

06/08/2021, 8:44 AM

i want a

class AA

with a property

x: Int

and a

class BB

with properties

x: Int

and

y: Int

where

BB

inherits from

AA

(alternative: inner class would be ok too in case thats the only option) i've tried the snippets below, but no success so far. i checked the guide but couldnt find what i need. how do i make this work?

Untitled_kt.cpp

Sourabh Rawat

06/09/2021, 11:33 AM

How can I register serializers for my custom Json object? I prefer not to specify serialisers all the time when calling

encodeToString

LastExceed

06/11/2021, 6:03 AM

can someone explain what i need to put into that string? the docs say

a unique name of the type that is being serialized

but i dont understand what that means also why does Line 2 work but Line 3 break ?

Untitled.cpp

CLOVIS

06/11/2021, 10:52 AM

If I add a primary constructor (

init

block) to a serialized data class, will it be executed on deserialization?

👌 1

CLOVIS

06/12/2021, 12:55 PM

Are they known bugs with sealed classes in 1.2.1 in JS/JVM?

val data: Data

where

Data

is a sealed class gives me

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"data": {
	"type": "SIMPLE",
	"id": "TEXT"
}

on JS, and

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"data": [
	"SIMPLE",
	{
		"id": "TEXT"
	}
]

on JVM, which unsurprisingly completely fails when Ktor tries to send messages between them.

Sourabh Rawat

06/12/2021, 1:34 PM

How can I handle extra fields when deserialising? For example, I have -

class Foo(val bar: String)

in. json I have

{ bar: 'asd', foobar: 'jkl', fb1: 'abc'}

I want to deserialise the above json into class Foo, but also be. able to access

foobar & fb1

, somehow. without having to add those fields in class Foo specifically. What I am looking for is something like

extraFields

map

Nikky

06/14/2021, 12:23 PM

seems like there is some weirdness with deeply nested arrays on jvm

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[[Ljava.lang.Object; cannot be cast to [[[D

it works fine on js or when downgrading to serialization

1.0.1

tthe affected types / typealiases are

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typealias PointCoordinates = DoubleArray
typealias MultiPointCoordinates = Array<PointCoordinates>
typealias LineStringCoordinates = Array<PointCoordinates>
typealias LinearRingCoordinates = Array<PointCoordinates>
typealias MultiLineStringCoordinates = Array<LineStringCoordinates> // Outer polygon + holes
typealias PolygonCoordinates = Array<LinearRingCoordinates> // Outer polygon + holes
typealias MultiPolygonCoordinates = Array<PolygonCoordinates>

it is for geojson out of the typeliases

PolygonCoordinates

and

MultiPolygonCoordinates

seem to be affected

Nikolay Kasyanov

06/14/2021, 2:11 PM

Hey folks 👋 while deserializing (implementing

KSerializer.deserialize

), is there a way to get access to the “raw” value of a primitive? As a string, for example. Since JSON numbers don’t have to be floating point numbers (by the standard https://www.json.org/json-en.html, although some implementation do assume that they are all double, unfortunately), I need a way to read fractional numbers from JSON without compromising their precision (to convert them to some decimal type, for example), none of the existing

Decoder

can do that it seems. Am I missing something? One option would be to write such values as strings server-side, but 1) it’s not always feasible to change existing endpoints that are just fine 2) one doesn’t always control the API. UPD found an issue, apparently it’s not possible atm: https://github.com/Kotlin/kotlinx.serialization/issues/1405

Jason Ankers

06/14/2021, 3:42 PM

Is serializing anonymous objects supported in kotlinx serialization? something like:

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@Serializable object {
    val message = "some message"
}