erase json object from a file

[barweizman]

I got a JSON file (written below), and I want to erase the JSON object with the given id "756746783" (this is the first object in the example), with all its self-other attributes(e.g address, email..), How can I do that?

[
{
"address": "ashdod",
"email": "[email protected]",
"emergency contact name": "alon",
"emergency contact phone": "0535500127",
"first name": "ron",
"id": "756746783",
"last name": "cohen",
"password": "77ik2331",
"phone": "0526732996",
"reset password details": ["olga", "06.11.1995", "tennis"],
"salary": 3000,
"type": "manager",
"user name": "ron87"
},
{
"address": "ashdod",
"email": "[email protected]",
"emergency contact name": "tal",
"emergency contact phone": "0548177765",
"first name": "nir",
"id": "11884398",
"last name": "levy",
"password": "68fnsd4",
"phone": "0578198932",
"reset password details": ["koral", "02.01.1989", "sleep"],
"salary": 4500,
"type": "manager",
"user name": "nir97"
}
]

[danielaparker]

Here's one way:

#include <jsoncons/json.hpp>
#include <fstream>

using jsoncons::json;

int main()
{
    try
    {
        // Read from input file
        std::ifstream is(/* pathname_to_input */);
 
        // If you want to preserve the order of members to be the same 
        // as in the original file, use ojson instead,
        json instance = json::parse(is);
 
        // Locate the item to be erased
        auto it = instance.array_range().begin();
        while (it != instance.array_range().end())
        {
            if (it->at("id").as<std::string>() == "756746783")
            {
                break;
            }
        }
 
        // If found, erase it
        if (it != instance.array_range().end())
        {
            instance.erase(it);
        }

        // Write to output file
        std::ofstream os(/* pathname_to_output */);

        instance.dump_pretty(os);
    }
    catch (const std::exception& e)
    {
        std::cout << e.what() << std::endl;    
    }
}

Here's another way using jsonpath:

#include <iostream>
#include <fstream>
#include <jsoncons/json.hpp>
#include <jsoncons_ext/jsonpath/jsonpath.hpp>

using jsoncons::ojson;
namespace jsonpath = jsoncons::jsonpath;

int main()
{
    std::ifstream is(/*path/to/input*/);

    ojson instance = ojson::parse(is);

    // Select all objects that have id not equal to '756746783' and return in an array 
    auto result = jsonpath::json_query(instance, "$.*[?(@.id != '756746783')]");

    std::cout << pretty_print(result) << "\n";

    std::ofstream os(/*path/to/output*/);
    result.dump_pretty(os);
}

[barweizman]

Definitely what I was looking for! This is my first time using json objects and working with json files, I searched everywhere and couldn`t find an appropriate example. I really recommend you to add this to the examples folder, very helpful.
Thank you!

[danielaparker]

It's been added Erase an object with a specified key from an array, and the examples folder. Thanks for the contribution.