c++ - Creating my own Iterators

Question

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.

Answer 1

/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.

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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.