C / C++ / MFC

9-May-09 6:03

Hi everyone. I have a rather simple(or so i thought) problem. I cant seem to pass, and recieve a pointer to a list.I need access to this list so i can add a newly created object(of the class sphere) into it!
I am calling a method of a class Sphere like this:

//sphere.h
class sphere{
int id, promjer, x, y;

  sphere(int idd, int ppromj, int xx, int yy, std::list<sphere> *llist_of_classes) //adding newly created object to the list, or so i thought
      : id(idd), promjer(ppromj), x(xx), y(yy){
		llist_of_classes.push_back(this);
}

//main.cpp
std::list<sphere> list_of_classes;

void main(){
...

  sphere Ball(1,2,3, &list_of_classes); //this is the point where i call the constructor to create the object, and add it to the list

}

I get the 'cannot convert paramater 5 from..to..' error msg. Does anyone have any idea how to solve this problem?
Or more generally, how do i pass and recieve pointers to std::list?!
thx!

Code-o-mat9-May-09 7:09

9-May-09 7:09

Isn't std::list a template, doesn't it need template arguments (type of list elements and such)? What is the exact error message you get?

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

Avion859-May-09 8:15

9-May-09 8:15

Yes it does, the code i supplied was not actual! for which i am sorry. Check out the code in an answer to a poster below!
thx!

Code-o-mat9-May-09 8:22

9-May-09 8:22

Ok, sorry for the nitpicking. Smile | :)

I believe your problem is that you should use llist_of_classes->push_back(this); instead of llist_of_classes.push_back(this); in the constructor of your sphere since it is a pointer not the object (or a reference to the object) itself.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

Avion859-May-09 8:26

9-May-09 8:26

i've tried before, and this is what i've got:

error C2664: 'std::list<_Ty>::push_back' : cannot convert parameter 1 from 'sphere *const ' to 'const sphere &'

but it does make sense what you are saying, the solution will probably have the '->'
thanks!

Code-o-mat9-May-09 8:49

9-May-09 8:49

Do you want to put pointers in that list? If your answer is yes then you probably need to change the template parameter for the std::list (something like std::list<my_class*> instead of std::list<my_class> i guess), if no, then you probably need to use ...pushback(*this); instead of pushback(this).

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

Avion859-May-09 8:56

9-May-09 8:56

You are right! i finally got it to work
the solution:

llist_of_classes->push_back(*this);

Thank you!

Code-o-mat9-May-09 9:00

9-May-09 9:00

No probs, glad i could help.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

Stephen Hewitt9-May-09 7:26

Stephen Hewitt

9-May-09 7:26

Firstly revise your post: you can't see any of the < or > characters or what's between them. Now to your problem, the constructor to your class looks like this:

sphere(int idd, int ppromj, int xx, int yy, std::list<sphere> *llist_of_classes)

That's four ints and a pointer to a std::list.
The code your having problems with looks like this:

Member 3885283 wrote:
sphere Ball(1,2,3, &list_of_classes);

Here you're passing three ints and a pointer to a std::list.

Steve

Avion859-May-09 8:12

9-May-09 8:12

First off, thanks for the reply. Now to the code. This is the actual code i should have posted earlier, this is the actual full code:
I am not sure what you mean by not being able to see whats between the <> and the brackets themselves? what am i doing wring?

//util.h   this is like globals.h
#include "stdlib.h"
#include "stdio.h"
#include "Sphere.h"
#include <list>

extern std::list<sphere>list_of_classes;
extern std::list<sphere>::const_iterator iterator;


//Sphere.h
#include <list>

class sphere{
public:
	int id;
	int promjer;
	int x;		//pos in world coordinates
	int y;		

	sphere(int idd, int ppromj, int xx, int yy, std::list<sphere> *llist_of_classes) : id(idd), promjer(ppromj), x(xx), y(yy){
		llist_of_classes.push_back(this);    //<-c2228 times 3!!
	};	
};

//main
#include "sphere.h"
#include "util.h"       //wich holds include<list> so its available

std::list<sphere>list_of_classes;
std::list<sphere>::const_iterator iterator;

void main(){

	sphere objekt(1,2,3,4,&list_of_classes); //     calling with the right number of arguments
	
        for(iterator=list_of_classes.begin(); iterator!=list_of_classes.end(); ++iterator)  //this simply writes objects data after creation
	{
		printf("kugla:%d, promjer: %d, x: %d, y: %d\n",iterator->id, iterator->promjer, iterator->x, iterator->y);
	} 

	getchar();
}

this code generates C2228:left of '.push_back' must have class/struct/union <-3times

This is the entire literal code.
All i need is a way to correctly pass a pointer to the list, add the newly created sphere object in its constructor into the list, and thats it!
Anyone spot the problem?

thank you!

Stuart Dootson9-May-09 8:35

Stuart Dootson

9-May-09 8:35

Avion85 wrote:
I am not sure what you mean by not being able to see whats between the <> and the brackets themselves? what am i doing wring?

You need to escape the < by replacing it with < - easiest way is to tick the 'Encode HTML tags when pasting' checkbox below the Text: field when pasting code into a message.

As to your problem...

llist_of_classes.push_back(this);

llist_of_classes is a pointer, not a reference or a value. So, the dot operator won't work with it - use the ->operator!

llist_of_classes->push_back(this);

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Avion859-May-09 8:55