Hi all,

I want to create a node with multiple attributes. It works by using SetAttribute multiple times but it looks like I cannot specify the order in which the attributes appear in the xml. The order of my SetAttribute calls has no influence on the order in the node. So my question is if there is a way to specify which attribute is the first, second and so on?

R.

Hi all, I want to create a node with multiple attributes. It works by using SetAttribute multiple times but it looks like I cannot specify the order in which the attributes appear in the xml. The order of my SetAttribute calls has no influence on the order in the node. So my question is if there is a way to specify which attribute is the first, second and so on?

The attributes are a set of name, value pairs. There is no order. xml parsers must work with any order.
Why do you need to order them?

Mattias

Why do you need to order them?

I don't need to, I just want to and the reason is simply aesthetics. So no big deal that it is not possible. Btw is there any comprehensible reason behind the order which SetAttribute uses? It is not alphabetical and not the order of the SetAttribute calls.

R.

Probably determined by hashvalue or the AVL tree order.

Michael.

Probably determined by hashvalue or the AVL tree order.

That makes sense, thank you for the info.

R.

No.
TDOMNamedNodeMap does not use hash nor AVL tree.
It uses a binary search in TDOMNamedNodeMap.Find to find the insert position, so it should be alphabetically sorted.
On a first glance the code looks ok.
Maybe Reimar can give an example when it does not work.

Mattias

Maybe Reimar can give an example when it does not work.

I am to lazy to attach the code, so here it is (you should know how to get it into Lazarus without too much hassle :) ):

program xmlattributes;
{$mode objfpc}{$H+}
uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes, SysUtils, CustApp,
  DOM, XMLWrite;
type
  { TXMLAttributes }
  TXMLAttributes = class(TCustomApplication)
  protected
    procedure DoRun; override;
  public
  end;

{ TXMLAttributes }

procedure TXMLAttributes.DoRun;
var
  ErrorMsg: String;
  Document: TXMLDocument;
  RootNode, Node: TDOMNode;
begin
  try
    Document:=TXMLDocument.Create;
    RootNode:=Document.CreateElement('ROOT');
    TDOMElement(RootNode).SetAttribute('someAttrib', 'someValue');
    Document.AppendChild(RootNode);
    RootNode:=Document.DocumentElement;
    Node:=Document.CreateElement('SomeNode');
    TDOMElement(Node).SetAttribute('aaaAttribute', '1');
    TDOMElement(Node).SetAttribute('aAttribute', '2');
    TDOMElement(Node).SetAttribute('ccAttribute', '4');
    TDOMElement(Node).SetAttribute('bAttribute', '3');
    RootNode.Appendchild(Node);
    WriteXMLFile(Document, 'test.xml');
  finally
    Document.Free;
  end;
  // stop program loop
  Terminate;
end;
var
  Application: TXMLAttributes;
{$R *.res}
begin
  Application:=TXMLAttributes.Create(nil);
  Application.Title:='XMLAttributes';
  Application.Run;
  Application.Free;
end.

cat test.xml
<?xml version="1.0"?>
<ROOT someAttrib="someValue">
<SomeNode aAttribute="2" bAttribute="3" ccAttribute="4" aaaAttribute="1"/> </ROOT>

Looks like the order is governed by the length of the attribute name first and then alphabetically.

R.

Thanks.

Yes, that is what CompareDOMStrings does.
Probably for speed reasons.
This function is fixed in the code.

Mattias

Actually it isn't sorted by length, but it's case-sensitive.

Mattias wrote

Yes, that is what CompareDOMStrings does. Probably for speed reasons.

Indeed, laz_xmlwrite and laz2_xmlwrite both do this, but the example is using xmlwrite.pas from fcl-xml.

This function is fixed in the code.

What do you mean?

Best regards.
Flávio

No. See

2.4.2/fpc/packages/fcl-xml/src/dom.pp

function CompareDOMStrings(const s1, s2: DOMPChar; l1, l2: integer):
integer;
var i: integer;
begin
  Result:=l1-l2;
  i:=0;
  while (i<l1) and (Result=0) do begin
    Result:=ord(s1[i])-ord(s2[i]);
    inc(i);
  end;
end;

No. laz_xmlwrite and laz2_xmlwrite use laz_dom, laz2_dom.

> This function is fixed in the code. > What do you mean?

The user can not change this behavior.

Mattias