JSON.mapping if "root" attribute has inherit keys

Question

I get response in for example next form:

resp = "{
  \"response\":
    {\"some\":
      {\"next\":
        {\"user\":
          {\"name\":\"Oleg\"}
        }
      }
    }
}"

I use JSON.mapping for combine user from JSON

struct User
  JSON.mapping(
    f_name: {type: String, key: "name", root: "WHAT.ABOUT.ROOT"}
  )
end

how I can use root attribute in this case, when I have inherit keys?

user = User.from_json(resp)

I tried root: "response.some.next.user" but it doesn't work

Thanks!

Answer 1

I found solution:

require "json"
private struct Response
  JSON.mapping(
    result: {type: Result, key: "get_users_response"}
  )  
end

private struct Result
  JSON.mapping(
    client: {type: Client, key: "get_users_result"}
  )
end

struct Client
  JSON.mapping(
    user: {type: User, key: "user"}
  )  
end

struct User
  JSON.mapping(
    id: {type: String, key: "id"},
    f_name: {type: String, key: "first_name"},
    l_name: {type: String, key: "last_name"}
  )
end

resp  = "{\"get_users_response\":{\"get_users_result\":{\"status\":\"Success\",\"error_code\":\"200\",\"user\":{\"id\":\"10\",\"first_name\":\"Oleg\",\"last_name\":\"Sobchuk\"}}}}"

response_container = Response.from_json(resp)
puts response_container
puts response_container.result.client.user

it looks a little difficult, but it works https://play.crystal-lang.org/#/r/1k3a

EDIT

According to THIS BENCHMARK with schema JSON parsing works little faster and use a much less memory.