Zig

Get the Content-ID of a Related Item

Demonstrates the Chilkat Email.GetRelatedContentID method, which returns the Content-ID of a related item (typically an image or style sheet embedded within an HTML email). The index is zero-based. This example loads an image from a file into a BinData object, adds it as a related item with AddRelatedBd (capturing the generated Content-ID and referencing it from the HTML), then reads that Content-ID back.

Background: The Content-ID is the anchor that ties an inline resource to the HTML that displays it: the body references cid: plus the ID, and the matching related part carries that same Content-ID. Because an image is binary, it is loaded into a BinData object (here from a file) and added with AddRelatedBd. Reading the Content-ID back lets a program verify or rewrite those links — for example when relocating embedded images or converting a message for display outside a mail client.

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Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    // Demonstrates the GetRelatedContentID method, which returns the Content-ID of a related
    // item.  Related items are typically images and style sheets embedded within HTML emails.
    // The index is zero-based.

    const email = try chilkat.Email.init();
    defer email.deinit();
    email.setSubject("GetRelatedContentID example");

    // Load the image data from a file into a BinData object.
    const bd_image = try chilkat.BinData.init();
    defer bd_image.deinit();
    bd_image.loadFile("qa_data/images/logo.png") catch {
        std.debug.print("{s}\n", .{try bd_image.getLastErrorText(alloc)});
        return;
    };

    // Add the image as a related item from the BinData; capture its generated Content-ID.
    const cid = email.addRelatedBd(alloc, "logo.png", bd_image) catch {
        std.debug.print("{s}\n", .{try email.getLastErrorText(alloc)});
        return;
    };

    // Reference the related item in the HTML body by its Content-ID.
    const sb_html = try chilkat.StringBuilder.init();
    defer sb_html.deinit();
    sb_html.append("<html><body><img src=\"cid:PLACEHOLDER_CID\"/></body></html>") catch {};
    _ = sb_html.replace("PLACEHOLDER_CID", cid);
    email.setHtmlBody(try sb_html.getAsString(alloc));

    // Read the Content-ID of the first related item (index 0).
    const cid0 = try email.getRelatedContentID(alloc, 0);
    std.debug.print("Related item 0 Content-ID: {s}\n", .{cid0});

    // Note: The path "qa_data/images/logo.png" is a relative local filesystem path,
    // relative to the current working directory of the running application.
}