import json struct Message { mut: id int text string reply_to &Message } struct OptionalMessage { mut: id int text string reply_to ?&OptionalMessage } fn test_main() { mut json_data := '{"id": 1, "text": "Hello", "reply_to": {"id": 2, "text": "Hi"}}' mut message := json.decode(Message, json_data)! assert message.reply_to.id == 2 json_data = '{"id": 1, "text": "Hello", "reply_to": {"id": 2, "text": "Hi", "reply_to": {}}}' message = json.decode(Message, json_data)! assert message.reply_to.reply_to.reply_to == unsafe { nil } json_data = '{"id": 1, "text": "Hello", "reply_to": {"id": 2, "text": "Hi", "reply_to": {"id": 5}}}' message = json.decode(Message, json_data)! assert message.reply_to.reply_to.id == 5 } fn test_recursive_optional_struct_ptr() { json_data := '{"id": 1, "text": "Hello", "reply_to": {"id": 2, "text": "Hi", "reply_to": null}}' message := json.decode(OptionalMessage, json_data)! reply := message.reply_to or { assert false return } assert reply.id == 2 assert reply.text == 'Hi' assert reply.reply_to == none }