Collectives™ on Stack Overflow

Find centralized, trusted content and collaborate around the technologies you use most.

Teams

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Using nlohmann json now, I've managed to store it and when I do a dump jsonRootNode.dump() , the contents are represented properly.

However I can't find a way to access the contents.

I've tried jsonRootNode["active"] , jsonRootNode.get() and using the json::iterator but still can't figure out how to retrieve my contents.

I'm trying to retrieve "active" , the array from "list1" and object array from "objList"

The following link explains the ways to access elements in the JSON. In case the link goes out of scope here is the code

#include <json.hpp>
 using namespace nlohmann;
 int main()
     // create JSON object
     json object =
         {"the good", "il buono"},
         {"the bad", "il cativo"},
         {"the ugly", "il brutto"}
     // output element with key "the ugly"
     std::cout << object.at("the ugly") << '\n';
     // change element with key "the bad"
     object.at("the bad") = "il cattivo";
     // output changed array
     std::cout << object << '\n';
     // try to write at a nonexisting key
         object.at("the fast") = "il rapido";
     catch (std::out_of_range& e)
         std::cout << "out of range: " << e.what() << '\n';
                Thanks that help me ! Can you just past the code you used to access key2 for example ? You can also mark this topic as resolved.
– RedLens834
                May 4, 2017 at 12:34
                @kayleeFrye_onDeck It's been a while since I've posted this :\ But I'm pretty sure there is an easy conversion for that
– Jeremy Kuah
                Aug 3, 2017 at 3:51
                @JeremyKuah, I ended up using get due to knowing the keys by-name and their value-type. Otherwise this would have been annoying... To handle it dynamically I was working around it by iterating the elements, but that was a sloppy hack.
– kayleeFrye_onDeck
                Aug 3, 2017 at 18:11
In case anybody else is still looking for the answer.. You can simply access the contents using the same method as for writing to an nlohmann::json object. For example to get values from 
json in the question:
  "active" : false,
  "list1" : ["A", "B", "C"],
  "objList" : [
      "key1" : "value1",
      "key2" : [ 0, 1 ]
just do:
nlohmann::json jsonData = nlohmann::json::parse(your_json);
std::cout << jsonData["active"] << std::endl;    // returns boolean
std::cout << jsonData["list1"] << std::endl;     // returns array
If the "objList" was just an object, you can retrieve its values just by:
std::cout << jsonData["objList"]["key1"] << std::endl;    // returns string
std::cout << jsonData["objList"]["key2"] << std::endl;    // returns array
But since "objList" is a list of key/value pairs, to access its values use:
for(auto &array : jsonData["objList"]) {
    std::cout << array["key1"] << std::endl;    // returns string
    std::cout << array["key2"] << std::endl;    // returns array
The loop runs only once considering "objList" is array of size 1.
Hope it helps someone
        
Thanks for contributing an answer to Stack Overflow!
Please be sure to answer the question. Provide details and share your research!
But avoid …
Asking for help, clarification, or responding to other answers.
Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.