How can I get more useful information from NSError?

Question

I want to get some useful information from NSError. If I print out [error userInfo], I get the following:

{
    NSFilePath = "/Users/apple/Library/Application Support/iPhone Simulator/5.1/Applications/08260B6A-4D65-48DF-ADD1-FFC8750081E8/Documents/abc";
    NSUnderlyingError = "Error Domain=NSPOSIXErrorDomain Code=17 \"The operation couldn\U2019t be completed. File exists\"";
}

I want to show the last line : "File exists", but how can i pick it out?

I tried:

localizedDescription
localizedFailureReason
localizedRecoverySuggestion
localizedRecoveryOptions
recoveryAttempter

Non of them show "File exists".

Answer 1

Finally, I follow code for perfect NSError print. Thanks @jbat100 and @Peter Warbo, I add a little bit on them code:

    NSDictionary *userInfo = [error userInfo];
    NSString *errorString = [[userInfo objectForKey:NSUnderlyingErrorKey] localizedDescription];