Re: [boost] API Review request: XML API for C++, second round

[Stefan Seefeld]

Hamish Mackenzie wrote:
Ok I think I understand the problem now.  What does node->document()
return and what does it point to???
it returns a dom::document_ptr, which behaves exactly the same way
as the other _ptr types, i.e. it has reference semantics.
Well I think as with the node->parent() it should return a proxy
object.  Something like...
that's what it does indeed.


// non owning reference
class document_ref
{
public:
  // Define document related methods here
protected:
  document_ref() : raw_( 0 ) {}
  xmlDoc * raw_;
};
// non owning pointer
class document_ptr
{
public:
  document_ptr( document_ref * );
  document_ref operator *() { return ref_; }
  document_ref * operator ->() { return &ref_; }
private:
  document_ref ref_;
};
// owning object with deep copy
class document : public document_ref
{
public:
  explicit document( const std::string & file );
  document( document_ref source )
  {
    // Deep copy here
  }
  ~document() { xmlFreeDoc( raw_ ); }
};
I don't really understand why we need three different classes to
manage documents. In particular I don't understand why you provide
a 'document_ptr' that is a wrapper around document_ref.
And I don't use a 'document' class, as that is managed implicitely
by my dom::document_ptr:
dom::document_ptr document; // create new document;
dom::document_ptr doc(document); // create second reference to it
dom::document_ptr doc2 = document.clone(); // clone it, i.e. make deep
                                              copy
root->document() can return document_ptr or document_ref.
indeed, that's what it does.



value_types could exist but it would require a deep copy to be
consistent.  If you do want to define it then I suggest
you mean if I do *not* want to define it ?


Yes, you could
1) define a deep copy value_type
that doesn't work as there is no way to copy nodes 'out of the
document'.
2) typedef void value_type;
3) leave it undefined

Your iterator types look good.  Why is there an extra level of
indirection in basic_element_const_iterator?
the const iterator is non-functional right now. I'v been wondering
how to provide one. It seems I would need to define a 'const_node_ptr'
set of classes.


I think that is right.  I would prefer it to be

typedef node_pointer< node_ref > node_ptr;
typedef node_pointer< const_node_ref > const_node_ptr;
In fact you will probably need const_ versions for all your reference,
pointer and iterator types. Though the pointers and iterators should
just be additional instances of template classes.
yes

Stefan



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