How to Append an Integer to a std::string in C ?

Appending an Integer to a std::string

The code below attempts to append an integer to a std::string using the append() method:

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

However, this code will result in a Debug Assertion Failure. This is because the append() method expects its argument to be a NULL-terminated string (char*).

There are several approaches to append an integer to a std::string:

1. std::ostringstream:

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

2. std::to_string (C 11 and later):

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

3. 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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