Delphi XML traversing

Question

Я новичок в Delphi.

Я хотел найти всех авторов по каждой теме.

Вот мой 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>

Answer 1

Вы можете использовать XPath, чтобы выбрать всех авторов, используя выражение, подобное этому //catalog/subject/book/author, из delphi у вас есть много вариантов для управления файлом XML, но в этом случае наиболее просто это использовать Microsoft XML DOM implementation

проверьте этот пример приложения

{$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.

наконец приложение вернет это

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