std::string::data() in C++

const char* data() const;
char* is the pointer to the obtained array.
Parameters : None

• std::string::data() returns an array that is owned by the string. Thus, the caller must not modify or free the memory. Let's take same example where ptr points to final array.

  ptr[2] = 'a';
  this will raise an error as ptr points to an array that
  is owned by the string, in other words ptr is now pointing
  to constant array and assigning it a new value is now not allowed.
  

• Return value of data() is valid only until the next call of a non-constant member function for the same string. Explanation : Suppose, str be the original string which is required to be converted in an array

  // converts str in an array pointed by pointer ptr.
  const char* ptr = str.data(); 
  
  // Bad access of str after modification
  // of original string to an array
  str += "hello"; // invalidates ptr
  
  // Now displaying str with reference of ptr
  // will give garbage value
  cout << ptr; // Will give garbage value
  

// CPP code to illustrate
// std::string::data()
 
#include <iostream>
#include <string>
#include <cstring>
using namespace std;
 
// Function to demonstrate data() 
void dataDemo(string str1)
{
    // Converts str1 to str2 without appending
    // '/0' at the end
    const char* str2;
    str2 = str1.data();
    
    cout << "Content of transformed string : ";
    cout << str2 << endl;
 
    cout << "After data(), length: ";
    cout << strlen(str2);
    
    
}
        
// Driver code
int main()
{
    string str("GeeksforGeeks");
 
    cout << "Content of Original String : ";
    cout << str << endl;
    cout << "Length of original String : ";
    cout << str.size() << endl;
   
    dataDemo(str);
 
    return 0;
}

Content of Original String : GeeksforGeeks
Length of original String : 13
Content of transformed string : GeeksforGeeks
After data(), length: 13