Η standard βιβλιοθήκη της C++ διαθέτει την κλάση std::string. Οποιοδήποτε αντικείμενο της κλάσης αυτής μπορείτε να το αντιμετωπίζετε σαν ένα δυναμικά μεταβαλλόμενο πίνακα από χαρακτήρες. Η κλάση string έχει το πλεονέκτημα ότι δεν χρειάζεται να σας απασχολεί η δέσμευση της απαραίτητης μνήμης για την αποθήκευση των αλφαριθμητικών.

Δείτε το παρακάτω παράδειγμα χρήσης της κλάσης string:

string.cpp

int main(int argc, char *argv[]) {
  string str = "Hello World!";
  cout << str  << endl;
  str.append(" How are you?");
  cout << str << endl;
 
  str = "Hello Wordl!";
  str += " How are you?";
  cout << str << endl;
}

Οι βασικές μέθοδοι της κλάσης string είναι οι εξής:

string();

string (const string& str);

string (const string& str, size_t pos, size_t len = npos);

string (const char* s);

string (const char* s, size_t n);

string (size_t n, char c);

Παράδειγμα χρήσης κατασκευαστών

strings_constructor.cpp

#include <iostream>
using namespace std;
 
int main() {
  string str = "Hello World!";
  string copy(str); 
  string substring(str, 0, 5);
  const char *p = str.c_str();
  string fromCString(p);
  string fromCSequence(p, 8);
  string fillwithDollars(5, '$');
 
  cout << str << endl;
  cout << copy << endl;
  cout << substring << endl;
  cout << p << endl;
  cout << fromCString << endl;
  cout << fromCSequence << endl;
  cout << fillwithDollars << endl;  
}

char& operator[] (size_t pos);
const char& operator[] (size_t pos) const;

char& at (size_t pos);
const char& at (size_t pos) const;

char& back();
const char& back() const;

char& front();
const char& front() const;

Στις όλες παραπάνω περιπτώσεις εάν το string είναι const επιστρατεύεται η const έκδοση της συνάρτησης.

string_fw_iterator.cpp

#include <iostream>
#include <string>
using namespace std;
 
int main (){
  string str = "Hello World!";
  for( string::iterator it=str.begin(); it!=str.end(); ++it)
    cout << *it;
  cout << endl;
}

string_rv_iterator.cpp

#include <iostream>
#include <string>
using namespace std;
 
int main (){
  string str = "Hello World!";
  for (string::reverse_iterator rit=str.rbegin(); rit!=str.rend(); ++rit)
    cout << *rit;
  cout << endl;
}

string& operator+= (const string& str);
string& operator+= (const char* s);
string& operator+= (char c);

string& append (const string& str);
string& append (const char* str);

string& assign (const string& str);
string& assign (const char* str)

string& insert (size_t pos, const string& str);
string& insert (size_t pos, const char* str);

string& erase (size_t pos = 0, size_t len = npos);
iterator erase (iterator p);
iterator erase (iterator first, iterator last);

string& replace (size_t pos,  size_t len,  const string& str);
string& replace (size_t pos,  size_t len,  const char* s);
string& replace (size_t pos,  size_t len,  const string& str,
                 size_t subpos, size_t sublen);

void swap (string& str);

append.cpp

#include <iostream>
#include <string>
using namespace std;
 
int main () {
  string str="Hello";
  string str2=" ";
  char[] str3="World";
  string str4 = "!\n";
 
  str+=str2;
  str.append(str3);
  str.append(str4);
  cout << str;
}

replace.cpp

#include <iostream>
#include <string>
using namespace std;
 
int main () {
  string base="this is a test string.";
  string str2="n example";
  string str3="sample phrase";
  string str4="useful.";
 
  string str=base;                // "this is a test string."
  str.replace(9,5,str2);          // "this is an example string." (1)
  str.replace(19,6,str3,7,6);     // "this is an example phrase." (2)
  str.replace(8,10,"just a");     // "this is just a phrase."     (3)
  cout << str << endl;
}

chicken.cpp

#include <iostream>
#include <string>
using namespace std;
 
main (){
  string chicken ("chicken");
  string egg ("egg");
  cout << "Before the swap, chicken comes from " << chicken;
  cout << " and egg comes from " << egg << endl;
 
  chicken.swap (egg);
  cout << "After the swap, chicken comes from " << chicken;
  cout << " and egg comes from " << egg << endl;
}

const char* c_str() const;

const char* data() const;

size_t copy (char* s, size_t len, size_t pos = 0) const;

size_t find (const string& str, size_t pos = 0) const;
size_t find (const char* str, size_t pos = 0) const;
size_t find (const char* str, size_t pos, size_t n) const;
size_t find (char c, size_t pos = 0) const;

size_t rfind (const string& str, size_t pos = npos) const;
size_t rfind (const char* str, size_t pos = npos) const;
size_t rfind (const char* str, size_t pos, size_t n) const;
size_t rfind (char c, size_t pos = npos) const;

string substr (size_t pos = 0, size_t len = npos) const;

int compare (const string& str) const;
int compare (size_t pos, size_t len, const string& str) const;
int compare (const char* str) const;
int compare (size_t pos, size_t len, const char* str) const;

cstring.cpp

#include <iostream>
#include <cstring>
#include <string>
using namespace std;
 
int main () {
  string str ("Split this sentence to word tokens");
  char * cstr = new char [str.length()+1];
  strcpy (cstr, str.c_str());
 
  char * p = strtok (cstr," ");
  while (p!=0) {
    cout << p << '\n';
    p = strtok(NULL," ");
  }
  delete[] cstr;
}