Pointer to a string - GameCreators Forum

Author

Message

Michael P

18

Years of Service

User Offline

Joined: 6th Mar 2006

Location: London (UK)

Posted: 17th Jun 2008 18:21

Link

I'm trying to create a pointer to a string, so that I can pass it to a function and that function can do a load of funky things to that string. Note that I don't want to simply pass a copy of a string to the function. I've tried various things with no luck, any ideas?

Here is some code that should demonstrate what I am trying to do:

+ Code Snippet

#include <iostream>
#include "string"

using namespace std;

void TestFunction(string * sText)
{
	cout << sText << "\n";
}

void main(void)
{
	string * Pointer = "Text";
	TestFunction(Pointer);
	int Blank;
	cin >> Blank;
}

Back to top

Profile PM Email

Mahoney

16

Years of Service

User Offline

Joined: 14th Apr 2008

Location: The Interwebs

Posted: 17th Jun 2008 18:30

Link

I think this will work. Hope it helps.

+ Code Snippet

#include <iostream>
#include <string>

using namespace std;

void TestFunction(char* szString)
{
        string sText ( szString );
	cout << sText << "\n";
}

void main(void)
{
	char* Pointer = "Text";
	TestFunction(Pointer);
	int Blank;
	cin >> Blank;
}

Back to top

Profile PM

Zotoaster

19

Years of Service

User Offline

Joined: 20th Dec 2004

Location: Scotland

Posted: 17th Jun 2008 18:35

Link

Why convert it to a string at all?

Don't you just hate that Zotoaster guy?

Back to top

Profile PM Email

Michael P

18

Years of Service

User Offline

Joined: 6th Mar 2006

Location: London (UK)

Posted: 17th Jun 2008 18:43

Link

Strings have saved me a lot of time with all of the functions that the library contains. I have amazed myself, and managed to get it to work whilst writing code to further explain what I am trying to do. I wanted to be able to direct a function to a string and let it perform operations on that string. The changes must not be lost once the function ends as would be the case with Mahoney's code. This now works fine:

+ Code Snippet

#include <iostream>
#include <string>

using namespace std;

// Create two different strings
string StringOne = "I am string one";
string StringTwo = "I am string two";

void TestFunction(string * sText)
{
	cout << *sText << "\n";

	*sText = ""; // Clear sText
}

void main(void)
{
	// Create pointers to the two strings
	string * PointerOne = &StringOne;
	string * PointerTwo = &StringTwo;

	// Run the function
	TestFunction(PointerOne);

	// See if the function worked
	cout << "StringOne: " << StringOne << "\n";
	cout << "StringTwo: " << StringTwo << "\n";

	int Blank;
	cin >> Blank;
}

Back to top

Profile PM Email

Michael P

18

Years of Service

User Offline

Joined: 6th Mar 2006

Location: London (UK)

Posted: 17th Jun 2008 19:01

Link

I've got another problem now: how do I gain access to the string operations using a pointer to a string

I tried (as a test operation):

*sText.erase(0,5);

Full code:

+ Code Snippet

#include <iostream>
#include <string>

using namespace std;

// Create two different strings
string StringOne = "I am string one";
string StringTwo = "I am string two";

void TestFunction(string * sText)
{
	cout << *sText << "\n";

	*sText.erase(0,5); // *** This does not work ***
}

void main(void)
{
	// Create pointers to the two strings
	string * PointerOne = &StringOne;
	string * PointerTwo = &StringTwo;

	// Run the function
	TestFunction(PointerOne);

	// See if the function worked
	cout << "StringOne: " << StringOne << "\n";
	cout << "StringTwo: " << StringTwo << "\n";

	int Blank;
	cin >> Blank;
}

Back to top

Profile PM Email

Mahoney

16

Years of Service

User Offline

Joined: 14th Apr 2008

Location: The Interwebs

Posted: 17th Jun 2008 19:48 Edited at: 17th Jun 2008 19:49

Link

Instead of *sText.erase(0,5), use this syntax:

+ Code Snippet

sText->erase(0,5);

-> is the syntax for pointers instead of a .

Back to top

Profile PM

Zotoaster

19

Years of Service

User Offline

Joined: 20th Dec 2004

Location: Scotland

Posted: 17th Jun 2008 19:57

Link

char* strings have to be pointers because they point to somewhere in memory (surprised?). They act kind of like an array.

std::strings don't need to be pointers. Simply doing "string MyString;" works fine.

Don't you just hate that Zotoaster guy?

Back to top

Profile PM Email

Sorry your browser is not supported!

Dark GDK / Pointer to a string