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(Delphi ActiveX) MIME Body vs. Sub-Parts
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.
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
mime: TChilkatMime;
part1: TChilkatMime;
success: Integer;
part2: TChilkatMime;
n: Integer;
part: IChilkatMime;
begin
// 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 := mime.GetPart(1);
Memo1.Lines.Add('Decoded Body:');
Memo1.Lines.Add(part.GetBodyDecoded());
Memo1.Lines.Add('Encoded Body:');
Memo1.Lines.Add(part.GetBodyEncoded());
end;
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