Delphi ActiveX

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.

Delphi ActiveX

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
mime: TChilkatMime;
part1: TChilkatMime;
part2: TChilkatMime;
n: Integer;
part: TChilkatMime;

begin
success := 0;

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

mime := TChilkatMime.Create(Self);

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

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

success := mime.NewMultipartMixed();
mime.UseMmDescription := 0;
success := mime.AppendPart(part1.ControlInterface);
success := mime.AppendPart(part2.ControlInterface);

// Show the MIME message:
Memo1.Lines.Add(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;
Memo1.Lines.Add('Num Parts = ' + IntToStr(n));
Memo1.Lines.Add('Body = ' + mime.GetBodyDecoded());

// The GetEntireBody retrieves the entire content after
// the header.  (Perhaps GetEntireBody should've been named
// GetEntireContent to make it less confusing...)
Memo1.Lines.Add('---- EntireBody:');
Memo1.Lines.Add(mime.GetEntireBody());
Memo1.Lines.Add('********');

// 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 := TChilkatMime.Create(Self);
mime.PartAt(1,part.ControlInterface);

Memo1.Lines.Add('Decoded Body:');
Memo1.Lines.Add(part.GetBodyDecoded());
Memo1.Lines.Add('Encoded Body:');
Memo1.Lines.Add(part.GetBodyEncoded());
end;