How should I handle a failure in an init: method in Objective-C?

Let's say I'm building a new class for the iPhone in Objective-C. In one of my init methods I want to manually allocate some memory. So, I might have something like this:

- (id)initWithSomeObject:(SomeObject *)someObject {
  self = [super init];
  if (self != nil) {
    myObject = someObject;
    [myObject retain];
    if ( (memory = calloc(1, sizeof(SomeStruct)) == NULL) {
      // What should I do here to clean up
      [self release];
      self = nil;
    }
  }
  return self;
}

Now, assuming that the calloc() could fail, and that failing to allocate memory is catastrophic for my object, what should I do inside the if-body to clean up properly? Is there an Objective-C idiom or pattern that I should be using?

Edit: I included the code posted by Rob Napier. But, I still have to release myObject, right? Or does the added code somehow trigger dealloc()?

Yes, you should release yourself and then return nil.

[self release];
self = nil;

See Issues with Initializers in the Concepts in Objective-C Programming guide.