I try to find a node with specific "node name", "attribute" and "attribute value". I use the recursive function below.
My XMLDocument has a node named 'TestNodeName' with attribute 'Format' with value '1'.
The function works fine the first time: returns the prower node.
When I call it a second time, it gives wrong results: returns a node that has a Format attribute having value 0.
Example of XML.
<mnode>
<TestNodeName ID="1" Format="0">
</TestNodeName>
<TestNodeName ID="2" Format="1">
</TestNodeName>
<TestNodeName ID="3" Format="0">
</TestNodeName>
<TestNodeName ID="4" Format="1">
</TestNodeName>
<TestNodeName ID="5" Format="0">
</TestNodeName>
</mnode>
End of XML
unit Unit4;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, XMLIntf, XMLDoc;
type
TForm4 = class(TForm)
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
//GLOBAL VARIABLES
var
Form4: TForm4;
XML:IXMLDocument;
mnode:IXMLNode;
s:string;
implementation
{$R *.dfm}
function RecursiveFindNode(ANode: IXMLNode; const SearchNodeName: string): IXMLNode;
var
I: Integer;
begin
if CompareText(ANode.NodeName, SearchNodeName) = 0 then
Result := ANode
else if not Assigned(ANode.ChildNodes) then
Result := nil
else begin
for I := 0 to ANode.ChildNodes.Count - 1 do
begin
Result := RecursiveFindNode(ANode.ChildNodes[I], SearchNodeName);
if Assigned(Result) then
Exit;
end;
end;
end;
function RecursiveFindNodeAttr(ANode: IXMLNode; const SearchNodeName: string; sAttr, sAttrVal:string): IXMLNode;
var
I: Integer;
sAttrFind: ixmlnode;
stext:string;
begin
sAttrFind:=ANode.AttributeNodes.FindNode(sAttr);
if sAttrFind<>nil then stext:=sAttrFind.Text else stext:='';
if (CompareText(ANode.NodeName, SearchNodeName)=0)and(CompareText(sAttrFind.NodeName, sAttr)=0)and(CompareText(stext, sAttrVal)=0) then
begin
Result := ANode;
end
else if not Assigned(ANode.ChildNodes) then
begin
Result := nil;
end
else begin
for I := 0 to ANode.ChildNodes.Count - 1 do
begin
Result := RecursiveFindNodeAttr(ANode.ChildNodes[I], SearchNodeName, sAttr, sAttrVal);
if Assigned(Result) then
begin
Exit;
end;
end;
end;
end;
procedure TForm4.FormCreate(Sender: TObject);
var
cnode,foundNode:IXMLNode; //<-- Problem here "foundNode" must be in global
begin
XML:= NewXMLDocument;
XML.LoadFromFile('C:\test.xml');
mnode:=XML.DocumentElement;
foundNode:=RecursiveFindNode(mnode,'TestNodeName');
//First time
cnode:=RecursiveFindNodeAttr(XML.DocumentElement,'TestNodeName','Format','1');
if cnode<>nil then
begin
cnode.Attributes['Format']:='5';
ShowMessage('ID='+cnode.Attributes['ID']);
end
else
ShowMessage('nil');
//Second time
foundNode:=RecursiveFindNodeAttr(XML.DocumentElement,'TestNodeName','Format','1');
if foundNode<>nil then
begin
foundNode.Attributes['Format']:='5';
ShowMessage('ID='+foundNode.Attributes['ID']);
end
else
ShowMessage('nil');
XML.SaveToFile('C:\test.xml');
end;
end.
After few test i finally found what caused wrong result of function. There was a similar recursive function. When i removed call of function all result was OK. RecursiveFindNode(ANode: IXMLNode; const SearchNodeName: string): IXMLNode;
In code bellow is call foundNode:=RecursiveFindNode(mnode,'TestNodeName'); The first call of RecursiveFindNodeAttr will give good result because of "cnode:=" The second call of RecursiveFindNodeAttr will give wrong result (ID=1) because i used same variable "foundNode:=RecursiveFindNodeAttr(..."
Finally when i moved "var foundNode:IXMLNode;" from Tform4 declaration to global the second call returned good result (ID=4)
I found another problem. when i use RecursiveFindNodeAttr in loop after replace all format="1" to format="5", the "foundNode" result remains "not nil" so loop will never end.
foundNode:=RecursiveFindNodeAttr(XML.DocumentElement,'TestNodeName','Format','1');
while foundNode<>nil do
begin
foundNode.Attributes['Format']:='5';
ShowMessage('ID='+foundNode.Attributes['ID']);
foundNode:=RecursiveFindNodeAttr(XML.DocumentElement,'TestNodeName','Format','1');
if foundNode=nil then ShowMessage('nil');
end;
