1 files changed, 59 insertions, 0 deletions
diff --git a/guide/example/example-json-27.kt b/guide/example/example-json-27.kt
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+++ b/guide/example/example-json-27.kt
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+// This file was automatically generated from json.md by Knit tool. Do not edit.
+package example.exampleJson27
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
+
+@Serializable(with = ResponseSerializer::class)
+sealed class Response<out T> {
+    data class Ok<out T>(val data: T) : Response<T>()
+    data class Error(val message: String) : Response<Nothing>()
+}
+
+class ResponseSerializer<T>(private val dataSerializer: KSerializer<T>) : KSerializer<Response<T>> {
+    override val descriptor: SerialDescriptor = buildSerialDescriptor("Response", PolymorphicKind.SEALED) {
+        element("Ok", dataSerializer.descriptor)
+        element("Error", buildClassSerialDescriptor("Error") {
+          element<String>("message")
+        })
+    }
+
+    override fun deserialize(decoder: Decoder): Response<T> {
+        // Decoder -> JsonDecoder
+        require(decoder is JsonDecoder) // this class can be decoded only by Json
+        // JsonDecoder -> JsonElement
+        val element = decoder.decodeJsonElement()
+        // JsonElement -> value
+        if (element is JsonObject && "error" in element)
+            return Response.Error(element["error"]!!.jsonPrimitive.content)
+        return Response.Ok(decoder.json.decodeFromJsonElement(dataSerializer, element))
+    }
+
+    override fun serialize(encoder: Encoder, value: Response<T>) {
+        // Encoder -> JsonEncoder
+        require(encoder is JsonEncoder) // This class can be encoded only by Json
+        // value -> JsonElement
+        val element = when (value) {
+            is Response.Ok -> encoder.json.encodeToJsonElement(dataSerializer, value.data)
+            is Response.Error -> buildJsonObject { put("error", value.message) }
+        }
+        // JsonElement -> JsonEncoder
+        encoder.encodeJsonElement(element)
+    }
+}
+
+@Serializable
+data class Project(val name: String)
+
+fun main() {
+    val responses = listOf(
+        Response.Ok(Project("kotlinx.serialization")),
+        Response.Error("Not found")
+    )
+    val string = Json.encodeToString(responses)
+    println(string)
+    println(Json.decodeFromString<List<Response<Project>>>(string))
+}