Create an object from path

[2rueSid]

Hi, @danielaparker! Thank you for creating such a great library.

I've encountered a minor problem related to a specific scenario.

Let's assume we have the following pseudocode:

jsoncons::json doc = '{"a": 5}';

std::string path = "$.b"; // potentially it may be any possible path

jsoncons::json new_obj = create_object_from_path(path); // {"b": "str"}
jsoncons::mergepatch::apply_merge_patch(value, new_obj); // {"a": 5, "b": "str"}

Currently, I'm considering creating a path parser or normalizer to obtain a vector of strings, or perhaps translating the path into JSONPointer notation and utilizing the add method.

I'm curious if there's a more elegant solution for implementing create_object_from_path that may already exist.

Thank you in advance!

[danielaparker]

Apologies for the late response. If your paths were represented by JSONPointers, you may be able to use the jsonpointer::replace function with the create_if_missing option, e.g.

#include <jsoncons/json.hpp>
#include <jsoncons_ext/jsonpointer/jsonpointer.hpp>

int main()
{
    jsoncons::json doc = jsoncons::json::parse(R"({"a": 5})");

    jsoncons::jsonpointer::json_pointer path("/b/c");

    std::error_code ec;
    jsoncons::jsonpointer::replace(doc, path, "str", true, ec);

   std::cout << pretty_print(doc) << std::endl;
}

Output:

{
    "a": 5,
    "b": {
        "c": "str"
    }
}

[danielaparker]

In version 0.172.0, you'll be able to write (currently supported on master)

#include <jsoncons/json.hpp>
#include <jsoncons_ext/jsonpointer/jsonpointer.hpp>
#include <jsoncons_ext/jsonpath/jsonpath.hpp>

int main()
{
    try
    {
        std::string str = R"($['b']['c'])"; // or "$.b.c"
        jsoncons::jsonpath::json_location location = jsoncons::jsonpath::json_location::parse(str);

        jsoncons::jsonpointer::json_pointer ptr{};
        for (const auto& element : location)
        {
            if (element.has_name())
                ptr /= element.name();
            else
            {
                ptr /= element.index();
            }
        }

        std::cout << "JSONPointer: " << ptr << std::endl;

        jsoncons::json doc = jsoncons::json::parse(R"({"a": 5})");

        jsoncons::jsonpointer::replace(doc, ptr, "str", true);

        std::cout << pretty_print(doc) << std::endl;
    }
    catch (const std::exception& e)
    {
        std::cerr << e.what() << std::endl;
    }
}

Output:

JSONPointer: /b/c
{
    "a": 5,
    "b": {
        "c": "str"
    }
}

[2rueSid]

Sorry for the late reply.
Thank you very much! This is exactly what we needed.