Skifte en string ud.

Hvis din streng er en char * eller et array af char's kan du bruge sprintf og strtol.

Et eksempel:

#include <cstdlib>
#include <cstdio>
#include <iostream>

int main(void)
{
  char s[124] = "123";
  int i = std::strtol(s, 0, 10);
  std::cout << "Som streng: " << s << std::endl;
  std::cout << "Som int: " << i << std::endl;
  i = 321;
  std::sprintf(s, "%d", i);
  std::cout << "Som streng: " << s << std::endl;
  std::cout << "Som int: " << i << std::endl;
  return 0;
}

Hvis det er en C++ streng (ie. std::string), må man omvejen omkring en stringstream:

#include <sstream>
#include <iostream>
#include <string>

int main()
{
  int i = 123;
  std::ostringstream os;
  std::string s;
  std::stringstream is;

  // Convert int to ostringstream
  os << i;
  // Then from ostringstream to string
  s = os.str();
  std::cout << "Som string " << s << std::endl;
  std::cout << "Som int " << i << std::endl;

  s = "321";
  // From string to stringstream
  is << s;
  // From stringstream to int
  is >> i;
  std::cout << "Som string " << s << std::endl;
  std::cout << "Som int " << i << std::endl;

  return 0;
}

man kan dog godt bruge:

int i = strtol(s.c_str(), 0, 0);

Men man kan ikke bruge sprintf, den anden vej.