XML. (was: Re: [ODE] outputting objects)

Chris Brodie Chris.Brodie at macquarie.com
Tue Feb 4 15:36:02 2003 

Not that my answer is the best but it was really easy for me(being new at the time) and newbies to understand:

I use a 1::1 mapping between elements and objects.

Element = Object
Attribute = Member Variable

So something like this:

<Body Position="0 0 0" Type="Box" Angle="0 45 0">
	<Geometry Type="Box"/>
<Body>

To me this is intuitive. The parent child relationship is quite intuitive and this would map to code in game like(In my c++ engine just as an example):

class CBody
{

	SetAttributes(Pairs& a_Attribs);

private:
	CVector			m_Position;
	std::vector<CGeometry> 	m_Geometry;
}

The only thing left to work out is, how the hell did the attribs get set? The parser collcts the pairs in to a 
std::map<std::pair<std::string, std::string> > >. For non c++ people thats a hash table of string pairs. A pair would be : Position="0 0 0"

So all the SetAttributes would have to do is :

(
	if (Attribs.Get("Position", Value) == true)
		m_Position = CVector(Value); // My vector can turn a string in to the numerical representation
}

I've used this for quite a while and it all works a charm. As for how the Objects get created I use a Factory class. For C people thats just a fancy lookup table. The table looks up the objects token, for example "Body" and create an object of that type.

An example of the factory can be found here:

http://www.flipcode.com/cgi-bin/msg.cgi?showThread=COTD-TemplateFactory&forum=cotd&id=-1



Here is a simple little world file from my engine, just a test world to test lighting:

<World Gravity="3.71">
	<Camera Position="0 2 0" />
	<Light Style="Directional" Position="50 50 50" />
	<StaticEntity Position="0 1 -70" Angle="0 0 0" File="Structure\Gastanks\1.lwo" />
</World>


..well thats how I do it anyway.

HTH

Chris
http:\\fourth.flipcode.com



-----Original Message-----
From: Anselm Hook [mailto:anselm@hook.org]


I'd still argue that the point is still not the xml itself - it is that
you need some tool to map between *any* notation and C objects.  lets say
that you have an xml file:

  <ode:body>
     <position>0 0 0</position>
  </ode:body>

how do you pluck out and apply position to the ode object without having
to hand write code?  do you write code like this:


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