将一个int附加到std :: string [英] Append an int to a std::string

问题描述

为什么此代码会导致Debug Assertion Fail？

Why is this code gives an Debug Assertion Fail?

   std::string query;
   int ClientID = 666;
   query = "select logged from login where id = ";
   query.append((char *)ClientID);

推荐答案

std :: string :: append（） 方法期望其参数为NULL （ char * ）。

有几种方法可以生成 string containg a int ：

There are several approaches for producing a string containg an int:

• std :: ostringstream

#include <sstream>

std::ostringstream s;
s << "select logged from login where id = " << ClientID;
std::string query(s.str());

std :: to_string （C ++ 11）

std::to_string (C++11)

std::string query("select logged from login where id = " +
                  std::to_string(ClientID));

boost :: lexical_cast

#include <boost/lexical_cast.hpp>

std::string query("select logged from login where id = " +
                  boost::lexical_cast<std::string>(ClientID));

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