From: "Morris, Chris" <chris.morris@...>
Date: 2002-03-19T22:53:44+09:00
Subject: RE: [ANN] Xml Serialization for Ruby

> <AddressBook>
>   <Entry>
>     <String name="firstname">John</String>
>     <String name="lastname">Doe</String>
>     <Address name="address">
>       <String name="street">Red Road, 6</String>
>       <Integer name="ZIP">98765</Integer>
>     </Address>
>   </Entry>
>   <Entry>
>     ...
>   </Entry>
> </AddressBook>
> 
> If you want to get all the addresses (and only them) from a file like
> this, you just have to wait for an <Address> element while parsing the
> XML source and marshal it.  If you relied on the top element, you'd
> have to marshal all the address book.  Depending on your application,
> this can be negligible as well as important.

Ah, much clearer now with the example. Good point. 

> ["John", /^G/, 12345]
> 
> It translated to:
> 
> <Array>
>   <String>John</String>
>   <Regexp>^G</Regexp>
>   <Integer>12345</Integer>
> </Array>
> 
> ...which you couldn't really express in this form:
> 
> <Array>
>   <attrname>
>    ...
>   </attrname>
> </Array> 

Again, another good point. Even with my typeless approach, array and hash
will have to have type elements ... well, no they wouldn't -- but we need
some way of delineating each element or key/value pair. Right now it's:

  <Array>
    <Element>thing</Element>
  <Array>

  <Hash>
    <Pair>
      <Key>thing</Key>
      <Value>other thing</Value>
    </Pair>
  </Hash>

I'd like to be able to squeeze those down somehow. 


> Hmmm, yes, you're right.
> 
> Yes, it does, and I get your point about not forcing it.

At least we're both making good points :) It's reinforcing the need to
support different approaches.

> Well, let us know about that, but if you find what feels a better
> approach than C#'s, then by all means go for it. :-)

Ha! Well, with my subsequent post and NaHi's post about how SOAP does it,
I'm convinced about the feel on a simple marshal. 

> Yes, that is not pretty at all, but some classes require special
> handling (arrays and the likes) and some other can be optimized (true,
> nil, false) so that is not too high a price to pay.

Yeah, I noticed that -- there is an advantage there to the true/false/nil
case. I'm not handling that now, so I'll have to check for those and change
them to the class versions like xmarshal does.


> I agree, that feels more OOP to me too.  My application had some
> requirements that prevented that:
> 
> - I did not know in advance what classes had to be marshallable;
> - even if I did, I could not create a marshaller object for each of
>   them because there were going to be a lot and performance would have
>   decreased;
> - I could not use a global object either, as the stuff needed to be
>   thread safe, and I could not use a mutex for the same 
> performance reasons.

Hmmm ... that's interesting. I can see with your first issue where my
approach just wouldn't work -- well, could you include the module into
Object?

  class Object
    include XmlSerialization
  end

The mods to the standard types would still work, and then everything (?)
gets to_xml from_xml?

As for the other two options, does the included module in Object handle
performance and threading issues? Because you wouldn't have all these
additional marshaling objects -- they're built into each object you already
have.

> I added Class, Regexp and Symbol, and yes, hashes containing other
> types can be marshaled.  The tests pretty much cover all the types it
> handles.

Cool.

Chris