1 files changed, 30 insertions, 0 deletions
diff --git a/guide/example/example-json-24.kt b/guide/example/example-json-24.kt
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+++ b/guide/example/example-json-24.kt
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+// This file was automatically generated from json.md by Knit tool. Do not edit.
+package example.exampleJson24
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+
+import kotlinx.serialization.builtins.*
+
+@Serializable
+data class Project(
+    val name: String,
+    @Serializable(with = UserListSerializer::class)
+    val users: List<User>
+)
+
+@Serializable
+data class User(val name: String)
+
+object UserListSerializer : JsonTransformingSerializer<List<User>>(ListSerializer(User.serializer())) {
+
+    override fun transformSerialize(element: JsonElement): JsonElement {
+        require(element is JsonArray) // this serializer is used only with lists
+        return element.singleOrNull() ?: element
+    }
+}
+
+fun main() {
+    val data = Project("kotlinx.serialization", listOf(User("kotlin")))
+    println(Json.encodeToString(data))
+}