Can't ad an object in another objet

[AlekGuedegbe]

Hi everybody,
I'am trying for a projet to add an object to another object like that :

json null;
null["enseignants"] = {};

      json j=
                 {
                     {"nom","popo"},{"prenom","zara"},{"id",12},{"vol_horraire",125.4}
                 };
                 

     null.insert(j.begin(), j.end());

            i wan't ad the object j into the object null without delete the content of the object null but it don't work ,

I'm on windows and i am using the last version of your library

Thanks.