Question

I’m having trouble finding examples of the correct way to use NSError, UIAlertView, and NSErrorRecoveryAttempting together on iOS. Most of the documentation and examples I can find cover the equivalent functionality on OS X, where the relevant behaviors are integrated by Cocoa. But in iOS it seems to be necessary do do this “by hand”, and I can’t find good examples of how it’s done.

I’d very much appreciate a few examples of best practice in using information in NSError to support recovery attempts from NSErrors reported to the user.

Answer 1

According to Apple’s documentation:

Important: The NSError class is available on both Mac OS X and iOS. However, the error-responder and error-recovery APIs and mechanisms are available only in the Application Kit (Mac OS X).

So, I’m not sure if you can use NSErrorRecoveryAttempting even though it does appear to be defined in the documentation (it looks like this is an area of the UIKit docs that have not yet been updated after being copied from AppKit’s documentation).

Here is how I handle errors in my code:

NSError *error = nil;
id result = [SomeClass doSomething:&error];

if (!result) {
    NSLog(@"Do something failed: %@", error);
    UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Something failed!" message:@"There was an error doing something." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil] autorelease];
    [alert show];
    return;
}