Access grandparent virtual method - c++

Question

Well, I have three classes:
template<typename E>
class Iterator {
public:
virtual ~Iterator() {
}
virtual bool hasNext() const = 0;
virtual const E& next() = 0;
};
template<typename E>
class IteratorPtr {
private:
Iterator<E>* iterator;
IteratorPtr(const IteratorPtr<E>&);
IteratorPtr<E>& operator=(const Iterator<E>&);
public:
IteratorPtr(Iterator<E>* it)
: iterator(it) {
}
~IteratorPtr() {
delete iterator;
}
Iterator<E>* operator->() const {
return iterator;
}
};
template<typename E>
class Collection
{
public:
virtual void add(const E & value) = 0;
virtual void add(const Collection<E>& collection);
virtual bool remove(const E& value) = 0;
virtual void clear() = 0;
virtual ~Collection()
{
}
virtual bool isEmpty() const = 0;
virtual int size() const = 0;
virtual bool contains(const E& value) const = 0;
virtual Iterator<E>* iterator() const = 0;
};
void Collection<E>::add(const Collection<E>& collection)
{
for (IteratorPtr<E> i(collection.iterator()); i->hasNext();) {
this->add(i->next());
}
}
Obs: all Set's methods are implemented.
template<typename E>
class Set;
template<typename E>
class SortedSet;
template<typename E>
class SetIterator;
template<typename E>
class SetNode {
private:
friend class Set<E> ;
friend class SortedSet<E> ;
friend class SetIterator<E> ;
SetNode()
: next(NULL) {
}
SetNode(E value)
: value(value), next(NULL) {
}
SetNode(E value, SetNode * next)
: value(value), next(next) {
}
~SetNode() {
}
private:
E value;
SetNode * next;
};
template<typename E>
class SetIterator: public Iterator<E> {
private:
friend class Set<E> ;
SetIterator(SetNode<E> * head)
: node(head) {
}
~SetIterator() {
}
bool hasNext() const {
return node != NULL;
}
const E & next() {
E& value = node->value;
node = node->next;
return value;
}
private:
SetNode<E> * node;
};
template<typename E>
class Set: public Collection<E> {
public:
Set(): numNodes(0), head(NULL) {
}
virtual ~Set() {
clear();
}
virtual void add(const E & value);
virtual bool remove(const E& value);
virtual void clear();
virtual bool isEmpty() const;
virtual int size() const;
virtual bool contains(const E& value) const;
virtual Iterator<E>* iterator() const;
private:
Set(const Set & obj): numNodes(0), head(NULL) {
}
virtual bool contains(const E & value, SetNode<E> * & previ) const;
protected:
int numNodes;
SetNode<E> * head;
};
template<typename E>
class SortedSet: public Set<E> {
private:
virtual bool contains(const E& value, SetNode<E> *& prev) const;
public:
SortedSet(): Set<E>() {
}
virtual void add(const E & value);
virtual ~SortedSet() {
this->clear();
}
};
Set and SortedSet don't implement add methods, cause they should do exactly what Collection::add(const Collection& c) does.
int main() {
Set<int> *s = new Set<int>();
s->add(10);
s->add(30);
s->add(12);
s->remove(10);
if (s->contains(30))
puts("Tem");
SortedSet<int> *ss = new SortedSet<int>();
ss->add(*s);
return 0;
}
but this code get a error in the line "ss->add(*s);", saying: no matching to ‘SortedSet::add(Set&)’
Why is this happening?

Answer 1

Now you've posted all the relevant code, the problem is that you've declared another function with the same name in Set:
virtual void add(const E & value);
This hides anything with the same name in the base class; so Collection::add is not accessible via a reference to Set or any of its subclasses.
To fix it, add a using-declaration to Set, to bring Collection::add into the scope of Set:
public:
using Collection::add;