XML strangeness

msdobrescu · Post by **msdobrescu** » Sat Apr 12, 2008 9:57 am

Hello,

First of all, I am a newbie to XML and I might do something wrong..
I have tried to use XML as config file. Then I faced the following issue:

Assume I have a structure like this:

<?xml version="1.0" encoding="utf-8"?>
<RootNode>
<Node2></Node2>
<Node1>node one text</Node1>
</RootNode>

I wish to have a null string in Node2 (i.e. "").

The wxXML* classes won't find any text node in Node2.

Ideally, I would make a difference between the <Node2/> and <Node2></Node2>, so in the first case I would have no text node in Node2 and in the second case, a text node having "" text inside. But this is not implemented in wxXML* classes.

wxXMLDocument class has the wxXMLDOC_KEEP_WHITESPACE_NODES flag that should not transform the node2 from <Node2></Node2> to <Node2/>. With this flag something annoying happens: some new lines are saved in the document.

This makes difficult to use the wxXML* classes for writing a configuration class, even those mentioned here http://wiki.wxwidgets.org/Development:_Todo_List are buggy because of that. They will create many <node/> entries in the same node in case of "" value of the text node.

What do you think?
How could it be done?

Yours,
Mike

Frank · Post by **Frank** » Sat Apr 12, 2008 12:08 pm

You can't.

The XML-Standard (see w3c.org) makes no difference between <node/> and <node></node>. It's just syntactic sugar for the same thing: An empty node.

If you want do have a diffence like eg '' and null in a database, you have to encode it on your own.

msdobrescu · Post by **msdobrescu** » Sat Apr 12, 2008 7:02 pm

Yes,

But why does it save <node></node> first, and next time <node/>?
Why doesn't it save <node>""</node> as other implementations?

Frank · Post by **Frank** » Sun Apr 13, 2008 12:57 pm

Because it's wrong.

<node>""</node> is the string "" (the two quote characters), not Empty.

If you want a "" for whatever reason, just set the value of the node to "\"\"" from C++.

Belgabor · Post by **Belgabor** » Sun Apr 13, 2008 1:24 pm

I also fail to see how any of this prevents you from writing a working xml-based conf implementation...

msdobrescu · Post by **msdobrescu** » Sun Apr 13, 2008 5:10 pm

Since there is no difference between having an empty text node and not having it at all...

Belgabor · Post by **Belgabor** » Mon Apr 14, 2008 6:48 pm

msdobrescu wrote:Since there is no difference between having an empty text node and not having it at all...

I don't understand, why is that a problem? Just implement the class and corresponding xml format in a way where that difference doesn't matter.