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Answer 1

+6 A:

Issue an HTTP GET request, don't follow the redirect, analyse the Location header. That's where the target of redirection is.

Specifically in Cocoa, use an asynchronous request with a delegate, handle the didReceiveResponse in the delegate. The first response will be the redirection one. Once you extract the URL in the handler, call [cancel] on the connection.

EDIT: depending on the provider, HEAD instead of GET might or might not work. And if you don't follow the redirect, the response data won't be loaded anyway, so there's no transmission overhead to having a GET.

Seva Alekseyev 2010-03-12 18:38:39

Answer 2

+2 A:

Do a HEAD and look for the Location header.

% telnet bit.ly 80
Trying 168.143.173.13...
Connected to bit.ly.
Escape character is '^]'.
HEAD /cwz5Jd HTTP/1.1
Host: bit.ly

HTTP/1.1 301 Moved
Server: nginx/0.7.42
Date: Fri, 12 Mar 2010 18:37:46 GMT
Content-Type: text/html; charset=utf-8
Connection: keep-alive
Set-Cookie: _bit=4b9a89fa-002bd-030af-baa08fa8;domain=.bit.ly;expires=Wed Sep  8 14:37:46 2010;path=/; HttpOnly
Location: http://www.engadget.com/2010/03/12/motorola-milestone-with-android-2-1-hitting-bulgaria-by-march-20/?utm_source=twitterfeed&amp;utm_medium=twitter
MIME-Version: 1.0
Content-Length: 404

calmh 2010-03-12 18:38:43

This ended up to be the most correct answer. The complete answer includes doing a head request as recommended in this answer by calmh. The response containing the location header can be extracted from the "connection willSendRequest...." delegate method, not the didReceiveResponse delegate method.

Run Loop 2010-03-13 03:09:04

HEAD does not always work, but GET generally does. The only caveat with GET is that the connection must be cancelled after url extraction to prevent downloading of the body (as suggested by Seva below)

Run Loop 2010-03-13 03:27:58

JK: You mean `connection:willSendRequest:redirectResponse:`. I thought your comment was wrong until I looked it up and saw the third component of the selector.

Peter Hosey 2010-03-13 05:37:21

Answer 3

+3 A:

LongUrlPlease offers an API which expands short urls.

Ben Griswold 2010-03-12 18:39:09

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