error trying to get to serialized subobject data

wuzamarine (5)
I am trying to write code that will retrieve the key value from "lasttradeprice" from this url -> http://pubapi.cryptsy.com/api.php?method=singlemarketdata&marketid=155

My code does not error during compile but at runtime I get the following error

testGetprice3.o: testGetprice3.cpp:71: int getData(): Assertion `document["success"].IsString()' failed.
Aborted


it would appear as though -> document.Parse(json.c_str()); is empty?

How do I retrieve the value of 'lasttradeprice'?


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#include "rapidjson/include/rapidjson/document.h"
#include <iostream>
#include <fstream>
#include <stdio.h>
#include <curl/curl.h>
#include <unistd.h>
#include <unordered_map>
#include <string>

using namespace rapidjson;

struct myData
{
        std::fstream *file;
        std::string *str;
};

size_t write_data(void *ptr, size_t size, size_t nmemb, myData *data)
{
        size_t numBytes = size * nmemb;

        if (data->file)
                data->file->write((char*)ptr, numBytes);

        if (data->str)
                *data->str += std::string((char*)ptr, numBytes);

        return numBytes;
}

//function to get coin data and perform analysis
int getData()
{
        int count = 0;

        //begin non terminating loop
        while(true)
        {
                count++;
                CURL *curl = curl_easy_init();
                if (curl)
                {
                        curl_easy_setopt(curl, CURLOPT_URL, "http://pubapi.cryptsy.com/api.php?method=singlemarketdata&marketid=155");

                        std::fstream file("/home/coinz/cryptsy/myfile.txt", std::ios_base::out | std::ios_base::ate);
                        std::string json;

                        myData data;
                        data.file = &file;
                        data.str = &json;

                        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &write_data);
                        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &data);

                        /* Perform the request, res will get the return code */
                        CURLcode res = curl_easy_perform(curl);

                        /* Check for errors */
                        if (res != CURLE_OK)
                        {
                                std::cerr << "curl_easy_perform() failed: " << curl_easy_strerror(res) << std::endl;
                        }
                        else
                        {
                                file << std::endl;

                                //begin deserialization
                                Document document;
                                document.Parse(json.c_str());
                                assert(document.HasMember("success"));
                                assert(document["success"].IsString());
                                //std::cout << "The Last Traded Price is = " << document["lasttradeprice"].GetString() << std::endl;
                        }

                        /* always cleanup */
                        curl_easy_cleanup(curl);
                }

                //timer for URL request.  *ADUJST ME AS DESIRED*
                usleep(10000000);
        }

        return 0;
}

//Le Main
int main(void)
{
        getData();
}

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