Lua

Add a Related String Resource to an Email

Demonstrates the Chilkat Email.AddRelatedString method, which adds a text-based related MIME resource, such as a style sheet, from an in-memory string and returns the generated Content-ID. The first argument is the MIME resource name, the second is the text content, and the third is the charset used to encode it. Because the Content-ID is generated by the call, this example adds the style sheet first, then builds an HTML body in a StringBuilder that references the style sheet by that cid:, and passes the result to SetHtmlBody.

Background: Related items are not always images loaded from disk — sometimes the resource is text you already have in memory, like a generated CSS style sheet or an SVG. AddRelatedString lets you embed such content directly without writing a temporary file first. As with other related items, it lives in the multipart/related enclosure and is referenced from the HTML by the Content-ID the method returns.

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Lua

local chilkat = require("chilkat")

-- Demonstrates the AddRelatedString method, which adds a text-based related MIME resource
-- (such as a style sheet) from an in-memory string and returns the generated Content-ID.
-- The first argument is the resource name, the second is the text content, the third is the charset.

local email = chilkat.Email.new()
email.subject = "Email with a related style sheet"

-- Add the text-based related resource first; capture the generated Content-ID.
local cid = email:add_related_string("styles.css", "body { color: navy; }", "utf-8")
if not email.last_method_success then
    print(email.last_error_text)
    return
end

-- 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.
local sbHtml = chilkat.StringBuilder.new()
sbHtml:append("<html><head><link rel=\"stylesheet\" href=\"cid:PLACEHOLDER_CID\"/></head><body>Styled content.</body></html>")
local numReplaced = sbHtml:replace("PLACEHOLDER_CID", cid)
email:set_html_body(sbHtml:get_as_string())

print("Related Content-ID = " .. cid)
print("NumRelatedItems = " .. email.num_related_items)