RapidJSON如何使用字符串变量查询对象

Question

I'm getting an error when I try to query an object using a string variable, but not when I directly use a string.

JSON: {"x": "hello"}

This works:

std::cout << document["x"].GetString();

This doesn't work:

std::string s = "x";
std::cout << document[s].GetString();

I'm getting this error:

error: no viable overloaded operator[] for type 'rapidjson::Document'
  (aka 'GenericDocument<UTF8<> >')
std::cout << document[s].GetString();
                ~~~~~^~
note: candidate function not viable: no known conversion from 'std::string'
  (aka 'basic_string<char, char_traits<char>, allocator<char> >') to 'SizeType' 
(aka 'unsigned int') for 1st argument

What am I doing wrong?

Answer 1

Try

std::cout << document[s.c_str()].GetString();

It seems the operator was not overloaded for a std::string but for a C-string.

(Reference for the c_str member function)