How to query in Json

[umardraz]

Hello

Here is my jSON object

{
    "id": 2,
    "groups": [
        {
            "gid": 2401,
            "name": "developers"
        },
        {
            "gid": 2402,
            "name": "devops"
        }
    ],
    "users": [
        {
            "gecos": "Umar Draz",
            "name": "umar",
            "need_update": "yes",
            "user_type": "admin",
            "status": "active"
        },
        {
            "gecos": "Imran Sharif",
            "name": "imran",
            "need_update": "yes",
            "user_type": "user",
            "status": "active"
        },
        {
            "gecos": "Irfan Sharif",
            "name": "irfan",
            "need_update": "yes",
            "user_type": "admin",
            "status": "active"
        }        
    ]
}

And In C# I can query on json object like this

var srchItem = UsersJSONObject.SelectToken("$.users[?(@.name == 'umar')]");

Then it return this in srchitem

{
   "gecos": "Umar Draz",
    "name": "umar",
    "need_update": "yes",
    "user_type": "admin",
     "status": "active"
},

Then I can easily access any key value from srchitem like this

Console.WriteLine(srchItem.name);

Would you please help me how I can do this in c++ using nlohmann

[nlohmann]

This library does not support that functionality (I think it's call JSON Path).

You would need to live with C++ algorithms. Assuming you parsed the JSON to variable j:

auto it = std..find_if(j["users"].begin(), j["users"].end(), [](const json& el) {
    return el["name"] == "umar";
});

if (it != j["users"].end())
{
    std::cout << (*it)["name"] << "\n";
}

(untested)

[umardraz]

Here is my function where I am trying to use it

std::string is_password_changed(json users, std::string name)
{
    
    std::string passwd;

    auto it = std::find_if(users["users"].begin(), users["users"].end(), [](const json& el) {
        return el["name"] == name;
    });

    if (it != users["users"].end())
    {
        passwd = (*it)["password"];
    }

    return passwd;

}

Now I am getting this error

new_fetch_linux_data.cpp: In lambda function:
new_fetch_linux_data.cpp:281:30: error: ‘name’ is not captured
         return el["name"] == name;
                              ^

How I can pass variable to return el["name"]

[nlohmann]

You need to add it to the capture of the lambda. Change your code to

    auto it = std::find_if(users["users"].begin(), users["users"].end(), [&name](const json& el) {
        return el["name"] == name;
    });

[umardraz]

Great, thanks