#include <iostream> #include <nlohmann/json.hpp> using json = nlohmann::json; int main() { try { // calling at() for a non-existing key json j = {{"foo", "bar"}}; json k = j.at("non-existing"); } catch (json::exception& e) { // output exception information std::cout << "message: " << e.what() << '\n' << "exception id: " << e.id << std::endl; } }