Objective-C

Get a Header Field from an Alternative Body

Demonstrates the Chilkat Email.GetAltHeaderField method, which returns the value of a header field within the Nth alternative body's MIME sub-part. The first argument is the zero-based alternative index; the second is the header field name. This example builds a message with plain-text and HTML alternatives and reads the Content-Type of the first alternative.

Background: A multipart/alternative message is a tree: each alternative body is its own MIME sub-part with its own little header block (Content-Type, Content-Transfer-Encoding, etc.). The top-level Email header methods read the message headers, whereas GetAltHeaderField reaches into a specific alternative's sub-part — useful for inspecting exactly how each representation is typed and encoded.

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Objective-C

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

//  Demonstrates the GetAltHeaderField method, which returns the value of a header field
//  within the Nth alternative body's MIME sub-part.  The 1st argument is the zero-based
//  alternative index; the 2nd is the header field name.

CkoEmail *email = [[CkoEmail alloc] init];

//  Create an email with plain-text and HTML alternatives.
[email SetTextBody: @"This is the plain-text alternative." contentType: @"text/plain"];
[email AddHtmlAlternativeBody: @"<html><body>This is the HTML alternative.</body></html>"];

//  Get the Content-Type header of the first alternative body (index 0).
NSString *ct = [email GetAltHeaderField: [NSNumber numberWithInt: 0] fieldName: @"Content-Type"];
NSLog(@"%@%@",@"Alternative 0 Content-Type: ",ct);