将两个字符串一起分配，获取访问读取冲突

我正在尝试将字符串传递给类突变器并将私有成员设置为该字符串 这是发送字符串的代码

void parseTradePairs(Exchange::Currency *curr, std::string *response, int begin, int exit)
{
    int start;
    int end;
    string temp;
    string dataResponse;
    CURL *tempCurl;
    initializeCurl(tempCurl);
    int location = response->find("marketid", begin);
    if(location <= exit)
    {
        start = location + 11;
        begin = response->find("label", start);
        end = begin - start - 3;
        findStrings(start, end, temp, response);
        getMarketInfo(tempCurl, temp, dataResponse);
        curr->_coin->setExch(temp); // here is the line of code that is sending the string
        dataResponse >> *(curr->_coin);
        curr->_next = new Exchange::Currency(curr, curr->_position + 1);
        parseTradePairs(curr->_next, response, begin, exit);
    }
}

这是 coin 类中的突变器，它接收字符串并将其分配给_exch

void Coin::setExch(string exch)
{
    _exch = exch;
}

我已经逐步浏览了它，并确保 exch 中有字符串。"105"，但一旦达到 _exch = exch;我收到阅读违规。我也尝试以指针身份传递。我认为它不应超出范围。并且类中的字符串变量在默认构造函数中初始化为零，但这同样很重要，除非我尝试从中读取而不是写入它。

/* defualt constructor */
Coin::Coin() 
{
    _id = "";
    _label = "";
    _code= "";
    _name = "";
    _marketCoin = "";
    _volume = 0;
    _last = 0;
    _exch = "";
}
Exchange::Exchange(std::string str)
{
    _exch = str;
    _currencies = new Currency;
    std::string pair;
    std::string response;
    CURL *curl;
    initializeCurl(curl);
    getTradePairs(curl, response);
    int exit = response.find_last_of("marketid");
    parseTradePairs(_currencies, &response, 0, exit);
}
int main(void)
{
    CURL *curl;
    string str;
    string id;
    Coin coin1;

    initializeCurl(curl);   
    Exchange ex("cryptsy");

    curl_easy_cleanup(curl);
    system("pause");
    return 0;
}
class Exchange
{
    public:
        typedef struct Currency
        {
            Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {}
            Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){}
            Currency() : _next(NULL), _prev(NULL), _position(0) {}
            Coin *_coin;
            Currency *_next;
            Currency *_prev;
            int _position;
        };
        /* constructor and destructor */
        Exchange();
        Exchange(std::string str);
        ~Exchange();
        /* Assignment operator */
        Exchange& operator =(const Exchange& copyExchange);
        /* Parse Cryptsy Pairs */
        friend void parseTradePairs(Currency *curr, std::string *response, int begin, int exit);
    private:        
        std::string _exch;
        Currency *_currencies;
};

这是我将其更改为修复它的内容。typedef 结构

{
            Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {}
            Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){}
            Currency()
            {
                _next = NULL;
                _prev = NULL;
                _position = 0;
                _coin = new Coin();
            }
            Coin *_coin;
            Currency *_next;
            Currency *_prev;
            int _position;
        };