Newb Question

[tycho61uk]

Hi, I'm having trouble writing the parser to read the following XML. What am I doing wrong?

--------- XML ---------
<?xml version="1.0" ?>
<Mesh>
    <!--Contents of Mesh-->
    <Vertices>
        <Vertex>
            <Position x="-0.724000" y="0.776000" z="0.104000" />
            <Normal x="0.000000" y="0.000000" z="0.000000" />
        </Vertex>
        <Vertex>
            <Position x="-0.716000" y="0.655000" z="0.194000" />
            <Normal x="0.000000" y="0.000000" z="0.000000" />
        </Vertex>
        <Vertex>
            <Position x="-0.721000" y="0.608000" z="0.056000" />
            <Normal x="0.000000" y="0.000000" z="0.000000" />
        </Vertex>
     ...more Vertex records...
    </Vertices>
</Mesh>
---------------------

TiXmlHandle handleDoc(&doc);
TiXmlElement* element;
TiXmlHandle handleRoot(0);
   
element = handleDoc.FirstChildElement().Element();
handleRoot = TiXmlHandle(element);
   
TiXmlElement *vertexElement = handleRoot.FirstChild("Vertices").FirstChild("Vertex").Element();
   
    for (vertexElement; vertexElement; vertexElement = vertexElement->NextSiblingElement("Vertex"))
    {   
        float x,y,z;
       
        TiXmlElement* positionElement = vertexElement.FirstChild("Position").Element();
       
        positionElement->QueryFloatAttribute("x",&x);
        positionElement->QueryFloatAttribute("y",&y);
        positionElement->QueryFloatAttribute("z",&z);
    }

I get the error that 'FirstChild' is not a member of TiXmlElement, but this can't be right because TiXmlElement is a subclass of TiXmlNode which defines that method.

Please help - this is driving me nuts!

[Lee Thomason]

> element = handleDoc.FirstChildElement().Element();

element should now point to <Vertices>, so this line is probably not what you meant to do:

> handleRoot = TiXmlHandle(element);

And this is doomed to fail:

> TiXmlElement *vertexElement = handleRoot.FirstChild("Vertices")

I think you just want to do this:

TiXmlHandle handleRoot( &doc );
TiXmlElement *vertexElement = handleRoot.FirstChild("Vertices").FirstChild("Vertex").Element();

lee

[tycho61uk]

Thanks Lee - that cleans up some code.

But it doesn't solve the main problem - I need to iterate  through the <vertex> records and examine the child elements <position> and <normal>. I can't do that currently because I can't call FirstChild() on the vertex element.

Please help!

[Lee Thomason]

The docs give 2 brief examples of iteration:

http://www.grinninglizard.com/tinyxmldocs/classTiXmlNode.html#a12

The easy way to go would be to "IterateChildren" on the <Vertices>, and then examine each <Position> and <Normal> with GetChildElement().

lee

[tycho61uk]

So is this a bug then? How come I can't call FirstChild() on my TiXmlElement when TiXmlElement descends from the class that defines that method?

[Lee Thomason]

No, there isn't a bug - I didn't read your XML carefully. Please read the code below to make sure I got it right, but the form is correct.

TiXmlElement* mesh = 0;
while ( mesh = doc->IterateChildren( "Mesh", vertex ) )
{
  TiXmlElement* vertices = 0;
  while ( vertices = mesh->IterateChildren( "Vertices", vertices ) ) {
    TiXxmlElement* vertex = 0;
    ...

etc. I think you see the form of it:
- Iterate over the Mesh
- Inner loop to iterate over the vertices
- Inner loop to iterate over the vertex
- Then use GetChildElement() to get the Position and the Normal
- Query the attributes of the Position and the Normal to get the values

Does that make sense?
lee

[tycho61uk]

Your code isn't quite correct,  but it led me in the right direction. Here's the routine - seems to work ok:
--------------------------------------
TiXmlDocument doc(pFilePath);
   
if (!doc.LoadFile()) {
return;
}
   
TiXmlNode* mesh = 0;
while ( mesh = doc.IterateChildren( "Mesh", mesh )) {

TiXmlNode* Vertices = 0;
while ( Vertices = mesh->IterateChildren( "Vertices", Vertices )) {

TiXmlNode* Vertex = 0;
while ( Vertex = Vertices->IterateChildren( "Vertex", Vertex )) {

TiXmlElement *position = Vertex->FirstChildElement("Position");
               
float x,y,z;
position->QueryFloatAttribute("x",&x);
position->QueryFloatAttribute("y",&y);
position->QueryFloatAttribute("z",&z);
               
....do something with position
               
TiXmlElement *normal = Vertex->FirstChildElement("Normal");
               
normal->QueryFloatAttribute("x",&x);
normal->QueryFloatAttribute("y",&y);
normal->QueryFloatAttribute("z",&z);

....do something with normal

}
}   
}
--------------------------------------

Thanks for developing TinyXML!