Good evening everybody,
I'm currently trying to understand the intrinsics of iterators in various languages i.e. the way they are implemented.
For example, there is the following class exposing the list interface.
template<class T>
class List
{
public:
virtual void Insert( int beforeIndex, const T item ) throw( ListException ) =0 ;
virtual void Append( const T item ) =0;
virtual T Get( int position ) const throw( ListException ) =0;
virtual int GetLength() const =0;
virtual void Remove( int position ) throw( ListException ) =0;
virtual ~List() =0 {};
};
According to GoF, the best way to implement an iterator that can support different kinds of traversal is to create the base Iterator class (friend of List) with protected methods that can access List's members. The concrete implementations of Iterator will handle the job in different ways and access List's private and protected data through the base interface.
From here forth things are getting confusing. Say, I have class LinkedList and ArrayList, both derived from List, and there are also corresponding iterators, each of the classes returns. How can I implement LinkedListIterator? I'm absolutely out of ideas. And what kind of data can the base iterator class retrieve from the List (which is a mere interface, while the implementations of all the derived classes differ significantly) ?
Sorry for so much clutter.
Thanks.
