Hi everyone I m consuming data from a JSON API Some response | Serialization

Hi everyone, I'm consuming data from a JSON API. Some responses contain decimal numbers. Depending in the culture-info field sent to the server, they might use dots (e.g. 18.312) or commas (e.g. 18,312) Is there some way I can interpret these both as Float in my Serializer class (Float only accepts dot notation)? Maybe through some custom field desserialization or something...?

Javier

1 year ago

you can create a custom serializer for example

Tiago Nunes

1 year ago

A custom serializer can receive a String and return a Float? How would I use it after creating it?

Can a custom serializer for certain fields only?

Oh I think i get it, I create a custom serializer, then I create a Serializable class CustomFloat with that serializer, and the fields will be of that type,right?

Javier

1 year ago

https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/serializers.md#primitive-serializer

Here you have a lot of examples

I would use a specific class for that

Do you need to handle that float in local?

Or you are only going to show that string in the UI?

Tiago Nunes

1 year ago

No, I'm not showing that string in the UI. I rather have it saved only as a Float and deal with Internationalization locally

Javier

1 year ago

then if it is a "real" float, I would create a custom class for that, but ideally backend should solve that

Tiago Nunes

1 year ago

Yeah but changing the backend is not an option, what you gona do 😒miling_face_with_tear:

@Javier I have this

object FloatAsDecimalString : KSerializer<Float> {
    override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("Float", PrimitiveKind.STRING)

    override fun serialize(encoder: Encoder, value: Float) =
        encoder.encodeString(value.toString())

    override fun deserialize(decoder: Decoder): Float =
        decoder.decodeString().replace(",", ".").toFloat()
}

@Serializable
data class ExampleResponse(
    val id: Long,
    val someDecimal: Float,
)

Now, how do I apply the Serializer?

Javier

1 year ago

@Serializable
data class ExampleResponse(
    val id: Long,
    @Serializable(with = FloatAsDecimalString::class) val someDecimal: Float,
)

I think with that

Tiago Nunes

1 year ago

Json.decodeFromString<ExampleResponse>("""
    {
        "id": 1,
        "someDecimal": "1.31"
    }
""")

This gave me an error: java.lang.ExceptionInInitializerError at com.qmx.web.contract.response.ExampleResponse$$serializer.deserialize(Unknown Source:64) at com.qmx.web.contract.response.ExampleResponse$$serializer.deserialize(ExampleResponse.kt:24) at kotlinx.serialization.json.internal.PolymorphicKt.decodeSerializableValuePolymorphic(Polymorphic.kt:63) at kotlinx.serialization.json.internal.StreamingJsonDecoder.decodeSerializableValue(StreamingJsonDecoder.kt:33) at kotlinx.serialization.json.Json.decodeFromString(Json.kt:85)

Javier

1 year ago

this is working for me

I changed the Float inside PrimitiveSerialDecriptor

Tiago Nunes

1 year ago

Why?

Wow it worked for me too changing to "id"

But why hahaha

Javier

1 year ago

I think because you cant use a type

you can change that to whatever you want,

sasdsadas

should work too

Tiago Nunes

1 year ago

There's probably a better descriptor for this use case then maybe? I don't know anything about descriptors yet...

Javier

1 year ago

probably that Serial name will create some code under the hood, and using Float or whatever existent type or reserved words is not a good idea

I usually put the original property name, in this case I would put

someDecimal

Tiago Nunes

1 year ago

I'll put DecimalString. I think it makes sense, its a DecimalString, which is a String, that's the description of the field i guess hahaha

Anyway, thanks a lot 🙌

🙂 1

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