CODEWITHSUNDEEP
c++jsonrapidjson
MIQUEAS GARCIA GONZALEZ
MIQUEAS GARCIA GONZALEZ

Reputation: 1

Handle JSON information with C++ and rapidjson

I have this JSON:

[{ "Country": "AFG", "Indicator": "NGDP_R", "Value": 183.26, "Year": 2002 }, {repeated struct across 3mb .json}]

I would like to store 'Country' values into a std::vector<string> countries; but I don't know how (I want to count how many different countries are in my JSON). There is what I've done so far:

std::ifstream ifs("../data/data.json");
if (!ifs.is_open())  {
    std::cerr << "Could not open file for reading!\n";
    return EXIT_FAILURE;
}
IStreamWrapper isw(ifs);
Document doc;
doc.ParseStream(isw);
StringBuffer buffer;
Writer<StringBuffer> writer(buffer);
doc.Accept(writer);
if (doc.HasParseError()){
  std::cout << "Error  : " << doc.GetParseError()  << '\n' << "Offset : " << 
  doc.GetErrorOffset() << '\n';
  return EXIT_FAILURE;
}

Could please somebody help me about how to handle this information and, if you could, explain me how to save into a 2D array like this?:

{ "Country": "AFG", "Indicator": "NGDP_R", "Value": 183.26, "Year": 2002 }
{ "Country": "AFG", "Indicator": "NGDP_R", "Value": 198.736, "Year": 2003 }
{ "Country": "AFG", "Indicator": "NGDP_R", "Value": 200.069, "Year": 2004 }
{ "Country": "AFG", "Indicator": "NGDP_R", "Value": 223.737, "Year": 2005 }
{ "Country": "AFG", "Indicator": "NGDP_R", "Value": 235.731, "Year": 2006 }
{ "Country": "AFG", "Indicator": "NGDP_R", "Value": 267.177, "Year": 2007 }...

Upvotes: 0

Views: 891

Answers (1)

Per Ghosh
Per Ghosh

Reputation: 533

Sample on how to iterate (json values that are array and object has iterators)

constexpr std::string_view stringJson = R"([ {"k1": "v1", "k2": "v2"}, {"k1": "v1", "k2": "v2"} ])";
rapidjson::Document documentJson;                                        // Create root rapidjson object
documentJson.Parse( stringJson.data() );

if( documentJson.IsArray() == true )                                     // Yes, we know it is an array :)
{
   for( const auto& itArray : documentJson.GetArray() )                  // iterate array
   {
      if( itArray.IsObject() == true )                                   // They are all objects
      {
         for( const auto& itObject : itArray.GetObject()  )
         {
            const auto& _name = itObject.name;                           // get name
            const auto& _value = itObject.value;                         // get value
            std::cout << _name.GetString() << " : " << _value.GetString() << "\n";// dump it
         }
      }
   }
}

Here is one tutorial. Click on RapidJSON chapter

Upvotes: 1

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