Lazarus Reading xml-with txmldocument and Txpathvariable

That is, the use of XPath, the specific syntax rules to see http://www.w3school.com.cn/xpath/xpath_syntax.asp, the explanation is quite detailed. Examples are given here to illustrate the specific application of the LAZARUS/FPC, as well as considerations. First, you can construct a "readxpath" function for easy invocation. After all, there are some tasks to be dealt with after each use of evaluatexpathexpression ....

View Plaincopy to Clipboardprint

2. function Readxpath (const anode:tdomnode; Const Apath: string   ): Tdomnode;
4. var   
6. rv:txpathvariable;
8. Tl:tfplist;
10. begin   
12. Result: = Nil   ;
14. if Assigned (anode) Then
16. begin
18. RV: = Evaluatexpathexpression (Apath, anode);
20. if Assigned (RV) Then
22. begin
24. tl: = RV .   Asnodeset;
26. if Assigned (TL) Then
28. begin
30. if tl. Count > 0 then
32. begin
34. Result: = Tdomnode (tl[0]);
36. end;
38. end;
40. end;
42. end;
44. End   ;

Specifically used, to remember that the return is actually "element", even if the mandatory Convention "property"--[@Attrib], so to read any value, you have to press "scan to Element" way to handle.

View Plaincopy to Clipboardprint

2. function readcfg: Boolean   ;
4. var   
6. .....
8. Vconfigxml: string  =  "'   ;
10. Historypath: string  =  "'   ;
12. Tracepath: string  =  "'   ;
14. Vxp:tdomnode;
16. .....
18. begin   
20. Result: = False;
22. Readxmlfile (XMLCFG, vconfigxml);
24. VXP: = Readxpath (XMLCFG, '/config/historypath[@value] ');
26. if Assigned (vXP) Then
28. begin
30. if vXP. HasAttributes Then   
32. Historypath: = VXP . Attributes . item[0].   NodeValue;
34. end;
36. VXP: = Readxpath (XMLCFG, '/config/tracepath[@value] ');
38. if Assigned (vXP) Then
40. begin
42. if vXP. HasAttributes Then   
44. Tracepath: = VXP . Attributes . item[0].   NodeValue;
46. end;
50. if (historypath <> ") and (Tracepath <> c7> ") Then
52. .....
56. End       ;

Lazarus Reading xml-with txmldocument and Txpathvariable