Filter JSON objects in a Array

[nyckmaia]

I would like to filter my json object, returning a json array with a filtered content.
Look this example below:

// Below is the 'originalJson' data content
{
    "myArray": 
    [
        {
            "key": "A",
            "name": "John"
        },
        {
            "key": "B",
            "name": "Steve"
        },
        {
            "key": "A",
            "name": "Roger"
        }
    ]
}

I would like to filter the JSON objects that have the key = A, I mean, excluding the "Roger" object.
Something like this:

const nlohmann::json jsonFiltered = originalJson["myArray"].filterKey("A");

So, inside the jsonFiltered should be:

[
    {
        "key": "A",
        "name": "John"
    },
    {
        "key": "A",
        "name": "Roger"
    }
]

Is it possible?
How can I do it?

My system:

• Ubuntu 20.04
• GCC 9.3.0

[nlohmann]

You can use any STL algorithm you like, e.g. std::copy_if:

#include <iostream>
#include "json.hpp"

using json = nlohmann::json;

int main()
{
    json j = R"({
    "myArray":
    [
        {
            "key": "A",
            "name": "John"
        },
        {
            "key": "B",
            "name": "Steve"
        },
        {
            "key": "A",
            "name": "Roger"
        }
    ]
})"_json;
    
    json filtered;
        std::copy_if(j["myArray"].begin(), j["myArray"].end(),
                     std::back_inserter(filtered), [](const json& item) {
                        return item.contains("key") && item["key"] == "A";
        });
    std::cout << filtered << std::endl;
}

Output:

[{"key":"A","name":"John"},{"key":"A","name":"Roger"}]

[nyckmaia]

Thank you!!

[FelixBenning]

For in-place filtering one can use the Erase-remove pattern