c++ - 将 int 附加到 std::string

Question

这个问题在这里已经有了答案:

How to concatenate a std::string and an int (24 个回答)

关闭 8 年前。

为什么这段代码会给出调试断言失败？

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

Answer 1

std::string::append()方法期望它的参数是一个以 NULL 结尾的字符串 (char*)。

有几种方法可以生成包含 int 的 string:

• 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::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));