Is it possible in c++ in an abstract class constructor to use a pointer of this abstract class as parameter?

Question

I've got an abstract class that represents an item of a tree. As this class already inherits from another (not abstract) class I want to use the same structure in the constructor as the base class:

class TreeItem //already given class
{
public:
    TreeItem(TreeItem *parent = 0);
    ...
};

class AbstractTreeItem : public TreeItem //class with some abstract methods
{
public:
    AbstractTreeItem(TreeItem *parent = 0);
    ...
};

But I want to assure that all classes which will inherit of my abstract class only have children of AbstractTreeItem, too. Therefore I would like to use a constructor like the following:

class AbstractTreeItem : public TreeItem
{
public:
    AbstractTreeItem(AbstractTreeItem *parent = 0);
    ...
};

And this is not possible as AbstractTreeItem is an abstract class. So is there a possiblity to achieve this in another way?

Answer 1

“this [using an AbstractTreeItem* argument] is not possible as AbstractTreeItem is an abstract class”

is incorrect.

I.e. there is no technical problem.

There does appear to be a design level problem, but that's a different kettle of fish.

Answer 2

So, you probably will have an non-abstract class:

class NonAbstractTreeItem : public AbstractTreeItem
{
public:
    NonAbstractTreeItem(AbstractTreeItem *parent = 0): AbstractTreeItem(parent) {
       ...
    }
    ...
};

that will be calling the AbstractTreeItem constructor.

If you want to underline that the constructor is only intended to be called from a child class, you can make it protected:

class AbstractTreeItem : public TreeItem
{
protected:
    AbstractTreeItem(AbstractTreeItem *parent = 0);
    ...
};