Objective-C

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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Objective-C

#import <CkoEmail.h>
#import <CkoBinData.h>
#import <NSString.h>
#import <CkoStringBuilder.h>

BOOL success = NO;

//  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.

CkoEmail *email = [[CkoEmail alloc] init];
email.Subject = @"GetRelatedContentID example";

//  Load the image data from a file into a BinData object.
CkoBinData *bdImage = [[CkoBinData alloc] init];
success = [bdImage LoadFile: @"qa_data/images/logo.png"];
if (success == NO) {
    NSLog(@"%@",bdImage.LastErrorText);
    return true;
}

//  Add the image as a related item from the BinData; capture its generated Content-ID.
NSString *cid = [email AddRelatedBd: @"logo.png" binData: bdImage];
if (email.LastMethodSuccess == NO) {
    NSLog(@"%@",email.LastErrorText);
    return true;
}

//  Reference the related item in the HTML body by its Content-ID.
CkoStringBuilder *sbHtml = [[CkoStringBuilder alloc] init];
[sbHtml Append: @"<html><body><img src=\"cid:PLACEHOLDER_CID\"/></body></html>"];
int numReplaced = [[sbHtml Replace: @"PLACEHOLDER_CID" replacement: cid] intValue];
[email SetHtmlBody: [sbHtml GetAsString]];

//  Read the Content-ID of the first related item (index 0).
NSString *cid0 = [email GetRelatedContentID: [NSNumber numberWithInt: 0]];
NSLog(@"%@%@",@"Related item 0 Content-ID: ",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.