C++ – Creating the own Iterators

c++iterator

I'm trying to learn C++ so forgive me if this question demonstrates a lack of basic knowledge, you see, the fact is, I have a lack of basic knowledge.

I want some help working out how to create an iterator for a class I have created.

I have a class 'Shape' which has a container of Points.
I have a class 'Piece' which references a Shape and defines a position for the Shape.
Piece does not have a Shape it just references a Shape.

I want it to seem like Piece is a container of Points which are the same as those of the Shape it references but with the offset of the Piece's position added.

I want to be able to iterate through the Piece's Points just as if Piece was a container itself. I've done a little reading around and haven't found anything which has helped me. I would be very grateful for any pointers.

Best Solution

/EDIT: I see, an own iterator is actually necessary here (I misread the question first). Still, I'm letting the code below stand because it can be useful in similar circumstances.


Is an own iterator actually necessary here? Perhaps it's sufficient to forward all required definitions to the container holding the actual Points:

// Your class `Piece`
class Piece {
private:
    Shape m_shape;

public:

    typedef std::vector<Point>::iterator iterator;
    typedef std::vector<Point>::const_iterator const_iterator;

    iterator begin() { return m_shape.container.begin(); }

    const_iterator begin() const { return m_shape.container.begin(); }

    iterator end() { return m_shape.container.end(); }

    const_iterator end() const { return m_shape.const_container.end(); }
}

This is assuming you're using a vector internally but the type can easily be adapted.