JSON

@derive(Json)

Auto-generate JSON serialization and deserialization:

@derive(Json)
class User {
    var name: String
    var age: Int
    var active: Bool
}

fun main() {
    let user = User { name: "Alice", age: 30, active: true }
    let json = user.toJson()
    println(json)
    // {"name":"Alice","age":30,"active":true}
}

JSON Type Constants

import core.json_derive

Constant	Value	Description
JSON_NULL	0	Null value
JSON_BOOL	1	Boolean
JSON_INT	2	Integer
JSON_FLOAT	3	Float
JSON_STRING	4	String
JSON_ARRAY	5	Array
JSON_OBJECT	6	Object

JSON Module

import json

JsonValue

The JsonValue class represents any JSON value. Constructors include JsonValue_nullValue, JsonValue_fromBool, JsonValue_bool, JsonValue_number, JsonValue_numberFloat, JsonValue_string, JsonValue_array, JsonValue_emptyArray, JsonValue_object, and JsonValue_emptyObject.

JSON Parser

Parse JSON strings:

import json.parser

let value = parseJson(jsonString)

JsonParser and JsonParseResult expose parser state and success/error results for callers that need more control than a one-shot parse helper. In 0.9.1 the parser's string and number paths avoid the old per-character concatenation and full-number substring pass. Number conversion uses a runtime range parser, reducing allocation pressure in large JSON payloads.

JSON Builder

Build JSON programmatically:

import json.builder

JsonBuilder and JsonBuilder_new provide incremental JSON construction. The builder stores output in StringBuilder parts internally, so large objects and arrays grow linearly instead of repeatedly copying the whole JSON string.

Runtime JSON Functions

Function	Description
seen_json_parse(str)	Parse JSON string
seen_json_stringify(val)	Serialize to JSON string
seen_json_get_type(val)	Get value type
seen_json_get_int(val)	Extract integer
seen_json_get_float(val)	Extract float
seen_json_get_string(val)	Extract string
seen_json_get_bool(val)	Extract boolean
seen_json_array_length(val)	Get array length
seen_json_array_get(val, idx)	Get array element
seen_json_object_get(val, key)	Get object field

Example

@derive(Json)
class Config {
    var host: String
    var port: Int
    var debug: Bool
    var tags: Array<String>
}

fun main() {
    let config = Config {
        host: "localhost",
        port: 8080,
        debug: false,
        tags: ["web", "api"]
    }

    let json = config.toJson()
    println(json)
    // {"host":"localhost","port":8080,"debug":false,"tags":["web","api"]}
}