Difference between revisions of "LMDXML Tutorial"

Revision as of 20:32, 20 October 2009

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Example 1. Creating and saving document

 var
   aDoc: ILMDXmlDocument;
   anElem: ILMDXmlElement;
 begin
   // Create empty XML document with root element 'base'
   aDoc := LMDCreateXmlDocument('base');

   // Create 'elem1' element and add it as child node for root element
   anElem := aDoc.DocumentElement.AppendElement('elem1');

   // Add 'a1' and 'a2' attributes to 'elem1'
   anElem.SetAttr('a1', 'elem1 a1');
   anElem.SetAttr('a2', 'elem1 a2');

   // Add another element 'elem2'
   anElem := aDoc.DocumentElement.AppendElement('elem');
   anElem.SetAttr('a1', 'elem2 a1');
   anElem.SetAttr('a2', 'elem2 a2');

   // Save document to file
   aDoc.Save('Test.xml');
 end;

There is content of saved file: <xml>

<?xml version="1.0" encoding="windows-1251"?>
<base>
  <elem1 a1="elem1 a1" a2="elem1 a2"/>
  <elem2 a1="elem2 a1" a2="elem2 a2"/>
</base>

</xml>

Example 2. Reading and analyzing documents

External xml file to parse. Test.xml <xml>

<?xml version="1.0" encoding="window-1251"?>
<root>
  <elem1 a1="v1" a2="v2"> 1</elem1>
  <elem2 a1="v1" a2="v2"> 2</elem2>
</root>

</xml>

Delphi code <delphi>

var
  aDoc: ILMDXmlDocument;
  anElem2: ILMDXmlNode;
begin
  // Create empty XML document 
  aDoc := LMDCreateXmlDocument;

  // Read content from file
  aDoc.Load('Test.xml');

  // Show in Memo1 full text of xml that we read above
  Memo1.Lines.Text := aDoc.Xml;

  Memo1.Lines.Add('------------------------');

  // Search element with tag 'elem2'
  anElem2 := aDoc.DocumentElement.SelectSingleNode('elem2');

  // Show in Memo1 XML-text anElem2
  Memo1.Lines.Add(anElem2.Xml);

  Memo1.Lines.Add('------------------------');

  // Show in Memo1 value of 'a2' attribute from anElem2 element
  Memo1.Lines.Add(anElem2.GetAttr('a2'));
end;

</delphi>

Example 3. It shows how to save structures to xml

<delphi> type

   TSex =(sxMale, sxFemale);

type

   TAuthor = record
       FirstName: string;
       LastName: string;
       Sex: TSex;
   end;

type

   TBook = record
       ISBN: string;
       Title: string;
       Authors: array of TAuthor;
   end;

var

 LLibrary: array of TBook;

procedure WriteAuthor(AParent: ILMDXmlNode; AAuthor: TAuthor); begin

 with AParent.AppendElement('author') do
 begin
   with AppendElement('firstname') do
     AppendText(AAuthor.FirstName);
   with AppendElement('lastname') do
     AppendText(AAuthor.LastName);
   SetAttr('sex', GetEnumName(TypeInfo(TSex), ord(AAuthor.Sex)));
 end;

end;

procedure WriteBook(AParent: ILMDXmlNode; ABook: TBook); var

 i: integer;
 LAuthors: ILMDXmlElement;

begin

 with AParent.AppendElement('book') do
 begin
   with AppendElement('isbn') do
     AppendText(ABook.ISBN);
   with AppendElement('title') do
     AppendText(ABook.Title);
   LAuthors := AppendElement('authors');
   for i := Low(ABook.Authors) to High(ABook.Authors) do
     WriteAuthor(LAuthors, ABook.Authors[i]);
 end;

end;

procedure TForm9.Button1Click(Sender: TObject); var

 LXMLLib: ILMDXmlDocument;
 i: Integer;

begin

 SetLength(LLibrary, 3);
 LLibrary[0].ISBN := 'ISBN-10: 0586010807';
 LLibrary[0].Title := 'Foundation';
 SetLength(LLibrary[0].Authors, 1);
 LLibrary[0].Authors[0].FirstName := 'Isaac';
 LLibrary[0].Authors[0].LastName := 'Asimov';
 LLibrary[0].Authors[0].Sex := sxMale;

 LLibrary[1].ISBN := 'ISBN-10: 0553293370';
 LLibrary[1].Title := 'Foundation and Empire';
 SetLength(LLibrary[1].Authors, 1);
 LLibrary[1].Authors[0].FirstName := 'Isaac';
 LLibrary[1].Authors[0].LastName := 'Asimov';
 LLibrary[1].Authors[0].Sex := sxMale;

 LLibrary[2].ISBN := 'ISBN-10: 0543903508';
 LLibrary[2].Title := 'A Connecticut Yankee in King Arthurs Court';
 SetLength(LLibrary[2].Authors, 1);
 LLibrary[2].Authors[0].FirstName := 'Mark';
 LLibrary[2].Authors[0].LastName := 'Twain';
 LLibrary[2].Authors[0].Sex := sxMale;

 LXMLLib := LMDCreateXmlDocument('library');
 for i := Low(LLibrary) to High(LLibrary) do
   WriteBook(LXMLLib.DocumentElement, LLibrary[i]);
 LXMLLib.Save('library.xml');

end; </delphi>

Example 4. How to read XML with unknown structure an fill TTreeView with it

<delphi> procedure XMLToTreeView(const AFileName, AOptElement, AOptAttr: String; ATreeView: TTreeView); var

 LXMLDoc: ILMDXmlDocument;

 procedure FillTree(ARootElement: ILMDXmlNode; AParent: TTreeNode);
 var
   i: Integer;
   LCurrentNode: TTreeNode;
   LNode: ILMDXmlNode;
 begin
   for i := 0 to ARootElement.ChildNodes.Count - 1 do
   begin
     if (ARootElement.ChildNodes.Item[i].NodeType = LMD_NODE_ELEMENT) then
     begin
       LCurrentNode := ATreeView.Items.AddChild(AParent, ARootElement.ChildNodes[i].NodeName + ': ' + 
                                                ARootElement.ChildNodes[i].Text);
       LNode := ARootElement.ChildNodes[i].SelectSingleNode(AOptElement);
       if Assigned(LNode) then
         LCurrentNode.Text := Format('Has child element %s, ', [AOptElement]) + LCurrentNode.Text;
       if ARootElement.ChildNodes[i].AttrExists(AOptAttr) then
       begin
         LCurrentNode.Text := Format('Has the "%s" attribute, ', [AOptAttr]) + LCurrentNode.Text;
       end;
       FillTree(ARootElement.ChildNodes[i], LCurrentNode);
     end;
   end;
 end;

begin

 LXMLDoc := LMDCreateXmlDocument();
 LXMLDoc.Load(AFileName);
 FillTree(LXMLDoc.DocumentElement, nil);

end; </delphi>