Can't find my constructor

I'm trying to compile a program I made, however, I keep getting an error form MSVC++ that one of my classes has no constructors. (Not that there is no appropriate constructor, it's telling me I don't even have one).

Here's the definition for the class (it's part of a linked list):

Code:

class InvTail : public InvItem
{
public:
	InvTail(InvItem *);
	virtual ~InvTail() {}
	...
private:
};

// prev and next are inherited from InvItem
InvTail::InvTail(InvItem *head)
{
	prev = head;
	next = 0;
}

The only place the InvTail constructor is called from is the InvHead constructor. (The head creates the tail, you know the drill). All the constructor does is try and create a new InvTail on the heap and pass it's this pointer as the argument.

Code:

InvHead::InvHead()
{
	next = new InvTail(this);
}

If I change "next = new InvTail(this);" to "next = new InvTail();" it tells me it can't find an appropriate constructor, (as I would expect), but as it is it gives simply tells me that there isn't a constructor, and the compile fails. Any help would be appreciated.

You probably called the constructor before you defined your class.

IE you probably did this:

class InvTail;

// Some stuff here

InvHead::InvHead()
{
next = new InvTail(this);
}

// Then after that you did

class InvTail : public InvItem
{
// blah blah blah
};

Ok, heres some more code:

Code:

class InvItem;	// linked list superclass
class InvHead;	// head
class InvTail;	// tail

// INVITEM
class InvItem
{
public:
	InvItem();
	virtual ~InvItem() { delete next; }	// don't delete prev because prev calls the deconstructer while deconstructing itself

	InvItem *getNext() { return next; }
	InvItem *getPrev() { return prev; }
protected:
	InvItem *next, *prev;
};

InvItem::InvItem():
prev(0),
next(0)
{}

// INVHEAD
class InvHead : public InvItem
{
public:
	InvHead();
	virtual ~InvHead() {}	// InvItem deconstructor cleans up
private:
};

InvHead::InvHead()
{
	next = new InvTail(this);
}

// INVTAIL
class InvTail : public InvItem
{
public:
	InvTail(InvItem *);
	virtual ~InvTail() {}
private:
};

InvTail::InvTail(InvItem *head)
{
	prev = head;
}

That's the code for the head and tail with just their constructors + deconstructors included. I still get the error though, so I think that should be enough. (At this point this is most of the code anyways).

Originally posted by Polymorphic OOP
You probably called the constructor before you defined your class.

Yeah, that's it. I assumed prototyping the class at the beginning of the file would let me do that. Sense that doesn't work, is there any way I can write it so that I CAN write my classes/member functions in an arbitrary order?

You always have to have a declaration of a function before you call it whether it be a constructor of some other member function -- just like when you work with nonmember functions.

So you can define your member functions in any order you want, just make sure you have declarations for the functions before you call them (IE define the class first).

As long as you define all of your methods in cpp's and you #include the definitions of the classes in that file, you should be fine.