converting std::string to const chars?
 

Hullo, I need help here I can't get this to work. I'm not sure if the code is correct. Any help would be most appreciated. I basically wanna convert a std::string to a const char array.

#include <string>

#include <iostream>



void bull(char[]);



int main()

{

   std::string Yo_momma = "iz fat";

   

   bull(Yo_momma.c_str()); //<--error here

   

   std::cin.get();

   return 0;

}



void bull( char crap[] )

{

    std::cout << crap;

}

My errors...

 In function `int main()': 

 invalid conversion from `const char*' to `char*' 

 initializing argument 1 of `void bull(char*)'

I'm using windows xp and Dev-cpp

God bless.

Re: converting std::string to const chars?
 

*Sigh* gotta love google.

char buf[255];

   

   std::strcpy( buf, Yo_momma.c_str() );

   bull(buf);

This works apparently?

Re: converting std::string to const chars?
 

c_str() returns a const char []. bull() takes a char [] as a parameter. That means that any changes made to char[] in bull() should be valid changes in c_str(). However since c_str() returns a const char [] it can't be changed. Therefore the compiler throws an error. Hence, you have to copy c_str() to a char [] before passing it to bull(). You could also try to temporarily ignore the constantness of c_str() when passing it to bull() by using the using the C++ syntax const_cast before the call c_str().

Re: converting std::string to const chars?
 

Assuming you won't in fact attempt to change 'crap' inside the 'bull' function, simply change the above to:

void bull( const char[] )

and

void bull( const char crap[] )

{

    std::cout << crap;

}

Re: converting std::string to const chars?
 

I know this works, but I don't know if it is a best practise.

#include <iostream>

#include <string>



void changeFirstLetter(char *str) {

    *str = 'J';

}



int main() {

    std::string msg = "Hello, world!";

    

    std::cout << msg << std::endl;

    changeFirstLetter(const_cast<char *>(msg.c_str()));

    std::cout << msg << std::endl;

}

OUTPUT:

Hello, world!

Jello, world!