This

[Amon Ra]

The keyword this represents within a class the address in memory of the object of that class that is being executed. It is a pointer whose value is always the address of the object.
It can be used to check if a parameter passed to a member function of an object is the object itself.

Taken from the cplusplus.com tutorial... I dont really understand what this sentence means...they give this example...i dont understand what's special about it...

//this
#include <iostream.h>

class CDummy
{
public:
	int isitme(CDummy& param);
};

int CDummy::isitme(CDummy& param)
{
	if(&param == this) return 1;
	else return 0;
}

void main()
{
	CDummy a;
	CDummy *b = &a;

	if(b->isitme(a))
		cout <<"yep, &a is b\n";
	else
		cout << "nope, don't know this one\n";
}

i am not sure what the this pointer is...
Thanks in advance!

[Amon Ra]

//this
#include <iostream.h>

class CDummy
{
public:
	int isitme(CDummy& param);
};

int CDummy::isitme(CDummy& param)
{
	if(&param == this) return 1;
	else return 0;
}

void main()
{
	CDummy a;
	CDummy *b = &a;

	if(b->isitme(a))
		cout <<"yep, &a is b\n";
	else
		cout << "nope, don't know this one\n";
}

What I dont get here, is what does the this pointer contain when i call the function: the address of *b or a?

[Amon Ra]

i dont knoe why, but the &param shows up as¶m =)

[parksie]

Hmm bizarre thing there

Anyway, this is a pointer to the instance of that class. What you're doing with the second one is you're passing a pointer rather than a class, so it shouldn't even compile

#include <iostream>

using namespace std; // Just making you standards-compliant :)

class CDummy {
public:
    int isitme(CDummy *param); // Using pointers instead, it's easier
};

int CDummy::isitme(CDummy *param) {
    if(param == this) return 1;
    return 0;
}

int main() {
    CDummy a;
    CDummy *b = &a;

    if(b->isitme(&a))
        cout <<"yep, &a is b\n";
    else
        cout << "nope, don't know this one\n";

    return 0;
}

That should print "yep, &a is b"

[kedaman]

he probably typed &param but it got &param
param is a reference, didn't you notice parksie? it should compile

[parksie]

CDummy a;
CDummy *b = &a;

if(b->isitme(a))

It's expecting a reference not a pointer Wouldn't passing a pointer violate the rules of referencing?

[kedaman]

Eh, well a is not a pointer right? if b is null (for some odd reason), it still fires isitme and pass a right?

[parksie]

Ok I can't read...I thought b was a

[kedaman]

hehehe

[parksie]

I really need to get a good monitor

[Amon Ra]

Thanks you very much guys!!