Pascal (Lazarus/Delphi)

MIME Body vs. Sub-Parts

See more MIME Examples

Explains the difference between sub-parts and body.

MIME documents (i.e. messages) can have a nested structure. The simplest MIME message contains a header followed by content (possibly encoded). The header is delimited from the content by two consecutive CRLF's.

A MIME message may be multipart. If so, then the Content-Type header field indicates "multipart" and the content the follows the header is itself a MIME message, which may also be multipart, etc. You can see how MIME messages effectively have a tree structure. The non-leaf nodes have Content-Types that are "multipart/" and the leaf nodes have non-multipart Content-Types.

The Chilkat MIME component/library uses two terms that need to be understood in order to effectively use the API. These are "body" and "sub-part". A multipart node has 1 or more sub-parts, but its body is empty. A leaf node (i.e. non-multipart node) has no sub-parts, but the body is (usually) non-empty.

This example creates a multipart MIME message and shows the results of getting the sub-parts and body of each node.

Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Mime;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  mime: TMime;
  part1: TMime;
  part2: TMime;
  n: Integer;
  part: TMime;

begin
  success := False;

  //  This example assumes the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  mime := TMime.Create;

  //  Create a multipart/mixed MIME message with two sub-parts.
  //  We'll use the Base64 encoding for the 2nd sub-part.
  part1 := TMime.Create;
  success := part1.SetBodyFromPlainText('This is part 1');

  part2 := TMime.Create;
  success := part2.SetBodyFromPlainText('This is part 2');
  part2.Encoding := 'base64';

  success := mime.NewMultipartMixed();
  mime.UseMmDescription := False;
  success := mime.AppendPart(part1);
  success := mime.AppendPart(part2);

  //  Show the MIME message:
  WriteLn(mime.GetMime());

  //  Here's the MIME:
  //  Content-Type: multipart/mixed;
  //  	boundary="------------040605030407000302060008";
  //  
  //  --------------040605030407000302060008
  //  Content-Type: text/plain;
  //  	 charset="us-ascii";
  //  Content-Transfer-Encoding: 7bit
  //  
  //  This is part 1
  //  --------------040605030407000302060008
  //  Content-Type: text/plain;
  //  	 charset="us-ascii";
  //  Content-Transfer-Encoding: base64
  //  
  //  VGhpcyBpcyBwYXJ0IDI=
  //  
  //  --------------040605030407000302060008--

  //  If we examine the root node of the MIME message, 
  //  we see that it has 2 sub-parts and the body is empty (as expected)
  n := mime.NumParts;
  WriteLn('Num Parts = ' + n);
  WriteLn('Body = ' + mime.GetBodyDecoded());

  //  The GetEntireBody retrieves the entire content after
  //  the header.  (Perhaps GetEntireBody should've been named
  //  GetEntireContent to make it less confusing...)
  WriteLn('---- EntireBody:');
  WriteLn(mime.GetEntireBody());
  WriteLn('********');

  //  Now examine the 2nd sub-part.  It has a body encoded
  //  using base64.  Get the contents of the body in both
  //  decoded and encoded forms:

  //  index 0 is the 1st part, index 1 is the 2nd part.
  part := TMime.Create;
  mime.PartAt(1,part);

  WriteLn('Decoded Body:');
  WriteLn(part.GetBodyDecoded());
  WriteLn('Encoded Body:');
  WriteLn(part.GetBodyEncoded());


  mime.Free;
  part1.Free;
  part2.Free;
  part.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.