Json: accessing json object as multimap

[Prati369]

I have a json file in this format. I want to access it . Ex: for key 'f' output should be 1. I tried many ways but unable to access it directly.

JSON file:
{
"1":"a", "2": [{ "a": [{ "b": [{ "c": [{ "d": [{ "e": { "f": "1", "g": "2" }, "h": [{ "i": "1", "j": "2" }], "j": { "l": "1", "m": 2 }, "n": { "o": "1", "p": 2 } }] }], }] }] } }

[nlohmann]

The value you posted is not valid JSON. Could you please double check?

[dota17]

Is ] missing before the last one '}'?
I added ']' there, and it would be fine:

{
    "1": "a",
    "2": [
        {
            "a": [
                {
                    "b": [
                        {
                            "c": [
                                {
                                    "d": [
                                        {
                                            "e": {
                                                "f": "1",
                                                "g": "2"
                                            },
                                            "h": [
                                                {
                                                    "i": "1",
                                                    "j": "2"
                                                }
                                            ],
                                            "j": {
                                                "l": "1",
                                                "m": 2
                                            },
                                            "n": {
                                                "o": "1",
                                                "p": 2
                                            }
                                        }
                                    ]
                                }
                            ]
                        }
                    ]
                }
            ]
        }
    ]
}

@Prati369, is this right?

[nickaein]

Possibly relevant to #1141.

You can f by chaining its parents, e.g.:

std::cout << json_object["2"]["a"]["b"]["c"]["d"]["e"]["f"]

or use JSON pointers

std::cout << json_object["/2/a/b/c/d/e/f"_json_pointer]

If the object hierarchy is not known beforehand, you can traverse the JSON object and look for the key. The following function is one simple way of doing that. Here is the working example: https://wandbox.org/permlink/Hlg3KIpxTSCdSPM8

nlohmann::json find_child_recursive(const nlohmann::json& j, std::string query_key)
{
    if(j.is_object())
    {
        for(const auto& [key, value]: j.items())
        {
            if(key == query_key)
            {
                return value;
            }
            else if(value.is_object() || value.is_array())
            {
                return find_child_recursive(value, query_key);
            }
        }
    }
    else if(j.is_array())
    {
        for(const auto& item: j)
        {
            return find_child_recursive(item, query_key);
        }
    }

    return nullptr;
}

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