[Lazarus] How is XMLConfig supposed to work?

[Mattias Gaertner]

On Wed, 27 Nov 2013 16:54:45 +0100
Frederic Da Vitoria <davitofrg at gmail.com> wrote:

> 2013/11/27 Frederic Da Vitoria <davitofrg at gmail.com>
> 
> > 2013/11/27 waldo kitty <wkitty42 at windstream.net>
> >
> >> On 11/27/2013 6:50 AM, Frederic Da Vitoria wrote:
> >>
> >>> Hello,
> >>>
> >>> I am trying to use XmlConfig to store simple configuration data, but I
> >>> can't
> >>> make it create a sensible Xml file. This is not really important in my
> >>> situation, as XmlConfig is able to correctly read back the strange data
> >>> it
> >>> wrote, but frustrating. I searched the web but could not find any
> >>> example. So
> >>> can anyone offer a working example of creating a xml file with XmlConfig?
> >>>
> >>
> >> can you provide a sample of what is being created and what you are
> >> expecting to actually see?
> >>
> >
> > I'm trying something like (just the minimum code, but I can give the
> > complete sources if it makes things easier):
> >
> > procedure TForm1.Button1Click(Sender: TObject);
> > const FILE_NAME = 'pXmlConfig.xml' ;
> > begin
> >   XmlConfig1.Filename := FILE_NAME ;
> > //  XmlConfig1.OpenKey ('/CONFIG') ;
> >   XmlConfig1.SetValue ('/CONFIG/L5', 'xx') ;
> >   XmlConfig1.SetValue ('/L1/L2', 'aa') ;
> >   XmlConfig1.SetValue ('/L1/L3', 'bb') ;
> >   XmlConfig1.SetValue ('/L1/L2', 'cc') ;
> >   XmlConfig1.SetValue ('/L8', 'dd') ;
> > //  XmlConfig1.CloseKey ;
> >   XmlConfig1.Flush
> > end;
> >
> > (No, it does not make any sense, just me trying to figure out how it
> > works.)
> >
> > And here is the result:
> >
> > <?xml version="1.0" encoding="utf-8"?>
> > <CONFIG L8="dd">
> >   <CONFIG L5="xx"/>
> >   <L1 L2="cc" L3="bb"/>
> > </CONFIG>
> >
> > The only thing which worked as I wanted is that SetValue ('/L1/L2', 'aa')
> > is overwritten by SetValue ('/L1/L2', 'cc')

The empty root '/' at the beginning is not needed.


> > - How do I create third level keys? (or is XmlConfig able to do more than
> > 2 levels?)

cfg.SetValue('/L1/L2/L3','value');


> > - Why does XmlConfig create L2, L3 and L5 as attributes ("/" usually is a
> > level separator, is it not) ?

TXMLConfig is a simple wrapper to store name/value pairs in xml.
You can access the full XML via cfg.Doc.


> > - More generally, is XmlConfig suited to do more than a simple list

You can store lists, trees, graphs as name/value pairs.


> > (which would be even less than a .ini can do)?

If you only use TXMLConfig and not the Doc then it can do the same as
a TIniFile. Of course there are speed and size differences.

 
> Now that I am thinking of it, I may be expecting too much. If XmlConfig
> handles more than 2 levels, then why stop to 3? And then, how would
> XmlConfig be different from a full Xml Implementation?

TXMlConfig uses a pretty complete XML parser/writer.
 
Mattias