[xsd-users] Extracting

[SHAH, Sima, FM]

We don't have access to the auto_pointer.  The contents of the iterator
return a reference.  Is there a way to get to the pointer?

Thanks,
Sima

P.S. Your new feature and factory mechanism idea is an excellent idea but
we'd like to be able to do this for all classes not just subclasses.

-----Original Message-----
From: Boris Kolpackov [mailto:boris at codesynthesis.com] 
Sent: 13 December 2005 15:57
To: SHAH, Sima, FM
Cc: 'xsd-users at codesynthesis.com'
Subject: Re: [xsd-users] Extracting


Hi,

SHAH, Sima, FM <Sima.SHAH at rbos.com> writes:

> I have an element defined as an xsi:type.  To extract it, I need to do 
> a dynamic cast which throws if not the correct type.
>
> Is there a way I can work out what the type is or a visitor pattern to 
> allow me to call a function given the correct type.

You can use dynamic_cast on a pointer instead of a reference. In that case
it will return 0 instead of throwing std::bad_cast. This is an effective way
to test if SomeType is-a SomeOtherType.

One extension that we are thinking about implementing is to allow you to
specify native C++ base classes for XML Schema types. For example, suppose
you have the following schema:

<complexType name="person" nativeBase="person_base">
  <sequence>
    <element name="name" type="xsd:string"/>
  </sequence>
</complexType>

<complexType name="superman">
  <complexContent>
    <extension base="person">
      <attribute name="can-fly" type="xsd:boolean" use="required"/>
    </extension>
  </complexContent>
</complexType>


And the person_base C++ class:

struct person_base
{
  ~person_base ();

  virtual
  ~print () = 0;
};

The generated code for the above schema fragment could look like this:

struct person: xml_schema::type, person_base
{
  string
  name () const;
};

struct superman: person
{
  bool
  can_fly () const;
};


Now, since print is pure virtual, you will need to implement those types:

struct person_impl: person
{
  virtual
  ~print ()
  {
    cout << "person " << name ();
  }
};

struct superman_impl: superman
{
  virtual
  ~print ()
  {
    cout << (can_fly () ? "flying superman " : "superman ") << name ();
  }
};

There would also be a factory mechanism that will allow one to instruct
parsing code to use person_impl and superman_impl for person and superman.
Is anybody interested in such a feature?


hth,
-boris


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