NSURLRequest: How to handle a redirected post?

Keep your original request, then provide your own willSendRequest:redirectResponse: to customize that request, rather than working with the one Apple provides you.

- (NSURLRequest *)connection: (NSURLConnection *)connection
             willSendRequest: (NSURLRequest *)request
            redirectResponse: (NSURLResponse *)redirectResponse;
{
    if (redirectResponse) {
        // The request you initialized the connection with should be kept as
        // _originalRequest.
        // Instead of trying to merge the pieces of _originalRequest into Cocoa
        // touch's proposed redirect request, we make a mutable copy of the
        // original request, change the URL to match that of the proposed
        // request, and return it as the request to use.
        //
        NSMutableURLRequest *r = [_originalRequest mutableCopy];
        [r setURL: [request URL]];
        return r;
    } else {
        return request;
    }
}

By doing this, you're explicitly ignoring some aspects of the HTTP spec: Redirects should generally be turned into GET requests (depending on the HTTP status code). But in practice, this behaviour will serve you better when POSTing from an iOS application.

See also:

• iOS Developer Library, URL Loading System Programming Guide: Handling Redirects and Other Request Changes

The HTTP specification for handling the 3xx class of status codes is very unfriendly towards protocols other than GET and HEAD. It expects some kind of user interaction for at the intermediary step of the redirection, which has lead to a plethora of incompatible client and server implementations, as well as a serious headache for web service developers.

From an iOS NSURL point of view, one of the things you might want to verify is that the original POST body is included in the new, redirect request.

Based off your comments on my original answer, and the edits to your question, it would appear that the URL you are trying to access has been updated permanently (301 status code). In which case you can actually avoid the redirects altogether by using the new URL.