Thread: C++ pointer to string error

this is a simple question that is quite straightforward.
i want to cout the second character in a pointed string (assuming only strings bigger than size [2] is passed in)
here is the code:

Code:

#include<iostream>

void main(void){

    std::string *asd=new std::string;

    *asd="asdfg";

    std::cout<<*asd[1];

}

and i have this error:

Code:

    1    IntelliSense: no operator "*" matches these operands
            operand types are: * std::string    c:\Users\samsung\Documents\Visual Studio 2012\Projects\ConsoleApplication3\ConsoleApplication3\Source.cpp    5    13    ConsoleApplication3

what's wrong?
help is appreciated!

I'm bad with C and C++, so I took this on for learning. Here's my code:

int main ()
{
std::string str="abcdef"; //the string
std::string *pointy =&str; // the pointer to the string
//get the object pointy is referencing, and call its substr
//method for the substr at position 2, of length 1
std::string str2 = (*pointy).substr (2,1);
std::cout << str2;
std::cout << '\n';

return 0;
}

Originally Posted by RamenNoodles

this is a simple question that is quite straightforward.
i want to cout the second character in a pointed string (assuming only strings bigger than size [2] is passed in)
here is the code:

Code:

#include<iostream>

void main(void){

    std::string *asd=new std::string;

    *asd="asdfg";

    std::cout<<*asd[1];

}

and i have this error:

Code:

    1    IntelliSense: no operator "*" matches these operands
            operand types are: * std::string    c:\Users\samsung\Documents\Visual Studio 2012\Projects\ConsoleApplication3\ConsoleApplication3\Source.cpp    5    13    ConsoleApplication3

what's wrong?
help is appreciated!

Did the formatting muck up your code because:

Code:

std::string *asd=new std::string;

certainly isn't going to compile

You're confusing C++ strings and C strings. If you're using C++ (and not trying to make something compatible with some old C library), just stick to C++ strings and forget the pointers. (Pointers are still important, but not here.)

For C++ strings:

Code:

std::string str = "asdf";
std::cout << str[2];

For C strings (still using C++ new and delete though):

Code:

char str[5] = "asdf";
std::cout << str[2];

I should mention I haven't tested these, but it's hard to mess the C++ version up.

thanks, i get that std::string is actually a class, and how do i access a function in the string object?

why do i have to use "->" for a non-array string pointer instead of using "." ?

cant i use mystring.erase(1,2) instead of mystring->erase(1,2)?

is there a specific reason?

If you have a std::string, then you'd use ".". If you've made a pointer to a string you'd use "->" which is actually just a shortcut to "(*ptr)." most of the time. The string class overloads the [] operator to pretend its an array of characters.