user writes access path to a nested element in a JSON file - c++

Question

I wrote a code that prompts the user for the access path to an element in a JSON file and then retrieves the value of that element. But I can only get access to a root element. What should user write to e.g. get object.array[2].field? I use single include nlohmann/json library.
My code:
using json = nlohmann::json;
int main() {
std::ifstream file("test3.json");
json data;
file >> data;
std::string access_path;
std::cout << "Enter the access path to the nested element (e.g. 'object.array[2].field'): ";
std::getline(std::cin, access_path);
try {
json nested_element = data.at(access_path);
std::cout << "Value of element: " << nested_element.dump() << std::endl;
} catch (json::out_of_range& e) {
std::cout << "Error: Invalid access path." << std::endl;
}
return 0;
}

Answer 1

First of all, you need a json_pointer.
json nested_element = data.at(json::json_pointer(access_path));
Then accessing field in array[2] in object would be entered by the user as
/object/array/2/field
Example version of the test3.json file:
{
"object": {
"array": [{
"field": "foo"
},
{
"field": "bar"
},
{
"field": "hello world"
}
]
}
}
Output:
Value of element: "hello world"