Xbase++

Add a Custom Header to a Related Item

Demonstrates the Chilkat Email.AddRelatedHeader method, which adds a custom MIME header field to an existing related item identified by its zero-based index. This example first adds a related style sheet (which becomes index 0) and captures its generated Content-ID, builds an HTML body that references the style sheet by that cid:, then attaches an extra header field to the related item and prints the resulting MIME.

Background: Like attachments, each related item (an inline image, style sheet, etc.) is a MIME part with its own small header block describing that part — Content-Type, Content-ID, Content-Location, and so on. AddRelatedHeader lets you insert additional fields into that per-part block, which is occasionally required for interoperability with clients that look for specific custom headers on embedded resources.

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LOCAL oEmail
LOCAL cCid
LOCAL oSbHtml
LOCAL nNumReplaced

//  Demonstrates the AddRelatedHeader method, which adds a custom MIME header field to an
//  existing related item, identified by its zero-based index.

oEmail := CreateObject("Chilkat.Email")
oEmail:Subject := "Related item with a custom header"

//  Add a related item first (a style sheet); capture its generated Content-ID.  It becomes
//  related-item index 0.
cCid := oEmail:AddRelatedString("styles.css", "body { color: black; }", "utf-8")
IF (oEmail:LastMethodSuccess == 0)
    ? oEmail:LastErrorText
    oEmail:destroy()
    RETURN
ENDIF

//  Build the HTML body, referencing the related style sheet by its Content-ID.  A
//  placeholder is used and then replaced with the actual Content-ID.
oSbHtml := CreateObject("Chilkat.StringBuilder")
oSbHtml:Append('<html><head><link rel="stylesheet" href="cid:PLACEHOLDER_CID"/></head><body>Styled content.</body></html>')
nNumReplaced := oSbHtml:Replace("PLACEHOLDER_CID", cCid)
oEmail:SetHtmlBody(oSbHtml:GetAsString())

//  Add a custom header field to the first related item (index 0).
oEmail:AddRelatedHeader(0, "X-Custom-Related-Header", "some value")

//  The custom header now appears in the related item's MIME part.
? oEmail:GetMime()

oEmail:destroy()
oSbHtml:destroy()