pointer in a class

[Shadowfiend]

I think the forward declaration has to look something like:

template <class T> class vector;

template <class T> class vector;

To copy to clipboard, switch view to plain text mode 

[wysota]

I'd say it should be "class vector<float>;". I don't see a reason to use a pointer to a vector in this situation, though... It's just asking for trouble and a necessity to write more code.

[mickey]

I'd say it should be "class vector<float>;". I don't see a reason to use a pointer to a vector in this situation, though... It's just asking for trouble and a necessity to write more code.

class vector<float>;
 
class Shape {
	const std::vector<float>* _sides;

class vector<float>;

class Shape {
	const std::vector<float>* _sides;

To copy to clipboard, switch view to plain text mode 

It doesn't compile; compile gets many error on the first line (like as I missed the ";").
I know It's unuseful, but I'd like compile it for study....
thanks.

[Shadowfiend]

Probably because you didn't put it in a namespace. Try:

namespace std { class vector<float>; }

namespace std { class vector<float>; }

To copy to clipboard, switch view to plain text mode 

or:

namespace std { template <class T> vector; }

namespace std { template <class T> vector; }

To copy to clipboard, switch view to plain text mode 

[mickey]

nothing to do

[wysota]

IMHO the pointer shouldn't be const.

[mickey]

IMHO the pointer shouldn't be const.

nothing to do again....

[wysota]

What do you mean by "nothing to do"?

[mickey]

What do you mean by "nothing to do"?

Sorry, my english is not correct.....It means that compiler gets the same errors (a lot) on the line "class vector<float>;" (I took off "const" as you suggested) . Of course, if I include vector.h, there aren't problems...I don't understand how to do this forward declaration

[Shadowfiend]

Sorry, I made a mistake in my template declaration. Try:

namespace std { template <class T> class vector; }

namespace std { template <class T> class vector; }

To copy to clipboard, switch view to plain text mode 

That compiles fine on my computer.

[mickey]

Sorry, I made a mistake in my template declaration. Try:

namespace std { template <class T> class vector; }

namespace std { template <class T> class vector; }

To copy to clipboard, switch view to plain text mode 

That compiles fine on my computer.

Maybe it can be the solution; but then, my problem is in a other place; try to compile this ,please (It doens't compile on .net2005)

//main.cpp
#include <iostream>
#include "forward.h"
#include <vector>
using namespace std;
 
int main (int argc, char argv[]) {
 
	Forward f;	
	vector<float>* fvec = new vector<float>; //EDIT <----------------------------
 
	return EXIT_SUCCESS;
}
//forward.h
#ifndef FORWARD_H
#define FORWARD_H
 
namespace std { template <class T> class vector; } 
// #include <vector> // with only this, all compiles
 
class Forward {
	std::vector<float>* _vec;
public:
	Forward();
	~Forward();
};
 
#endif FORWARD_H
 
//forward.cpp
#include "forward.h"
#include <vector>
using namespace std;
 
Forward::Forward() {
 
	_vec = new vector<float>;
}
Forward::~Forward() {}

//main.cpp
#include <iostream>
#include "forward.h"
#include <vector>
using namespace std;

int main (int argc, char argv[]) {

	Forward f;	
	vector<float>* fvec = new vector<float>; //EDIT <----------------------------

	return EXIT_SUCCESS;
}
//forward.h
#ifndef FORWARD_H
#define FORWARD_H

namespace std { template <class T> class vector; } 
// #include <vector> // with only this, all compiles

class Forward {
	std::vector<float>* _vec;
public:
	Forward();
	~Forward();
};

#endif FORWARD_H

//forward.cpp
#include "forward.h"
#include <vector>
using namespace std;

Forward::Forward() {

	_vec = new vector<float>;
}
Forward::~Forward() {}

To copy to clipboard, switch view to plain text mode 

[Shadowfiend]

Ah, that's right. std::vector takes an std::allocator as its second parameter. Well that just gets nasty...

Here's a place where this same issue is discussed: http://objectmix.com/c/251244-forwar...compliant.html

Looks like it's possible, but the advantage is negligible and there is not necessarily a guarantee that it will work.