Is it possible to prevent an NSURLRequest from caching data or remove cached data following a request?

Usually it's easier to create the request like this

NSURLRequest *request = [NSURLRequest requestWithURL:url
      cachePolicy:NSURLRequestReloadIgnoringCacheData
      timeoutInterval:60.0];

Then create the connection

NSURLConnection *conn = [NSURLConnection connectionWithRequest:request
       delegate:self];

and implement the connection:willCacheResponse: method on the delegate. Just returning nil should do it.

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse {
  return nil;
}

I have the same problem in my app when I requested info from twitter. In my case I didn't need to preserve those credentials, so I simple erase them using the next code:

- (void) eraseCredentials{
NSURLCredentialStorage *credentialsStorage = [NSURLCredentialStorage sharedCredentialStorage];
NSDictionary *allCredentials = [credentialsStorage allCredentials];

//iterate through all credentials to find the twitter host
for (NSURLProtectionSpace *protectionSpace in allCredentials)
    if ([[protectionSpace host] isEqualToString:@"twitter.com"]){
        //to get the twitter's credentials
        NSDictionary *credentials = [credentialsStorage credentialsForProtectionSpace:protectionSpace];
        //iterate through twitter's credentials, and erase them all
        for (NSString *credentialKey in credentials)
            [credentialsStorage removeCredential:[credentials objectForKey:credentialKey] forProtectionSpace:protectionSpace];
    }
}

I hope it works for somebody :)

If you use NSURLConnection take a look at the delegate:

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse

Return Value

The actual cached response to store in the cache. The delegate may return cachedResponse unmodified, return a modified cached response, or return nil if no cached response should be stored for the connection.