问题
I am new to Delphi.
I wanted to find all the authors under each subject.
Here is my XML
<?xml version="1.0"?>
<catalog>
<subject id="computer">
<book id="bk101">
<author>Gambardella, Matthew</author>
<title>XML Developer's Guide</title>
<genre>Computer</genre>
<price>44.95</price>
<publish_date>2000-10-01</publish_date>
<description>An in-depth look at creating applications
with XML.</description>
</book>
<book id="bk112">
<author>Galos, Mike</author>
<title>Visual Studio 7: A Comprehensive Guide</title>
<genre>Computer</genre>
<price>49.95</price>
<publish_date>2001-04-16</publish_date>
<description>Microsoft Visual Studio 7 is explored in depth,
looking at how Visual Basic, Visual C++, C#, and ASP+ are
integrated into a comprehensive development
environment.</description>
</book>
</subject>
<subject id="literature">
<book id="bk102">
<author>Ralls, Kim</author>
<title>Midnight Rain</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2000-12-16</publish_date>
<description>A former architect battles corporate zombies,
an evil sorceress, and her own childhood to become queen
of the world.</description>
</book>
<book id="bk103">
<author>Corets, Eva</author>
<title>Maeve Ascendant</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2000-11-17</publish_date>
<description>After the collapse of a nanotechnology
society in England, the young survivors lay the
foundation for a new society.</description>
</book>
<book id="bk104">
<author>Corets, Eva</author>
<title>Oberon's Legacy</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2001-03-10</publish_date>
<description>In post-apocalypse England, the mysterious
agent known only as Oberon helps to create a new life
for the inhabitants of London. Sequel to Maeve
Ascendant.</description>
</book>
<book id="bk105">
<author>Corets, Eva</author>
<title>The Sundered Grail</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2001-09-10</publish_date>
<description>The two daughters of Maeve, half-sisters,
battle one another for control of England. Sequel to
Oberon's Legacy.</description>
</book>
<book id="bk106">
<author>Randall, Cynthia</author>
<title>Lover Birds</title>
<genre>Romance</genre>
<price>4.95</price>
<publish_date>2000-09-02</publish_date>
<description>When Carla meets Paul at an ornithology
conference, tempers fly as feathers get ruffled.</description>
</book>
<book id="bk107">
<author>Thurman, Paula</author>
<title>Splish Splash</title>
<genre>Romance</genre>
<price>4.95</price>
<publish_date>2000-11-02</publish_date>
<description>A deep sea diver finds true love twenty
thousand leagues beneath the sea.</description>
</book>
<book id="bk108">
<author>Knorr, Stefan</author>
<title>Creepy Crawlies</title>
<genre>Horror</genre>
<price>4.95</price>
<publish_date>2000-12-06</publish_date>
<description>An anthology of horror stories about roaches,
centipedes, scorpions and other insects.</description>
</book>
<book id="bk109">
<author>Kress, Peter</author>
<title>Paradox Lost</title>
<genre>Science Fiction</genre>
<price>6.95</price>
<publish_date>2000-11-02</publish_date>
<description>After an inadvertant trip through a Heisenberg
Uncertainty Device, James Salway discovers the problems
of being quantum.</description>
</book>
<book id="bk110">
<author>O'Brien, Tim</author>
<title>Microsoft .NET: The Programming Bible</title>
<genre>Computer</genre>
<price>36.95</price>
<publish_date>2000-12-09</publish_date>
<description>Microsoft's .NET initiative is explored in
detail in this deep programmer's reference.</description>
</book>
<book id="bk111">
<author>O'Brien, Tim</author>
<title>MSXML3: A Comprehensive Guide</title>
<genre>Computer</genre>
<price>36.95</price>
<publish_date>2000-12-01</publish_date>
<description>The Microsoft MSXML3 parser is covered in
detail, with attention to XML DOM interfaces, XSLT processing,
SAX and more.</description>
</book>
</subject>
</catalog>
回答1:
You can use XPath to select all the authors, using a expression like this //catalog/subject/book/author, from delphi you have a lot of options to manage a XML file, but in this case the most easy is use the Microsoft XML DOM implementation
check this sample application
{$APPTYPE CONSOLE}
uses
ActiveX,
Variants,
ComObj,
SysUtils;
procedure ReadXMLFile(const FileName:TFileName);
const
Msxml2_DOMDocument='Msxml2.DOMDocument.6.0';
var
XmlDoc : OleVariant;
Nodes : OleVariant;
lNodes : Integer;
i : Integer;
begin
//create an instance to the XML DOM
XmlDoc := CreateOleObject(Msxml2_DOMDocument);
try
XmlDoc.Async := False;
//load the file
XmlDoc.Load(FileName);
//set the xpath mode
XmlDoc.SetProperty('SelectionLanguage','XPath');
//check for errors in the xml file
if (XmlDoc.parseError.errorCode <> 0) then
raise Exception.CreateFmt('Error in Xml Data %s',[XmlDoc.parseError]);
//select the nodes with match with the expression
Nodes := XmlDoc.selectNodes('//catalog/subject/book/author');
//get the number of nodes selected
lNodes:= Nodes.Length;
Writeln(Format('%d Authors found',[lNodes]));
//traverse the nodes
for i:=0 to Nodes.Length - 1 do
Writeln(Format('Author Name %s',[Nodes.Item(i).Text]));
finally
XmlDoc :=Unassigned;
end;
end;
begin
try
CoInitialize(nil);
try
ReadXMLFile(ExtractFilePath(ParamStr(0))+'test.xml');
finally
CoUninitialize;
end;
except
on E:Exception do
Writeln(E.Classname, ':', E.Message);
end;
Writeln('Press Enter to exit');
Readln;
end.
finally the application will return this
12 Authors found
Author Name Gambardella, Matthew
Author Name Galos, Mike
Author Name Ralls, Kim
Author Name Corets, Eva
Author Name Corets, Eva
Author Name Corets, Eva
Author Name Randall, Cynthia
Author Name Thurman, Paula
Author Name Knorr, Stefan
Author Name Kress, Peter
Author Name O'Brien, Tim
Author Name O'Brien, Tim
来源：https://stackoverflow.com/questions/5968467/delphi-xml-traversing