Why passing &error instead of error in Cocoa programming?

Question

In Cocoa programming, when dealing with NSError, why we are passing &error to a message instead of error?

NSError *error;
if (![managedObject.managedObje         


        

Answer 1

It's the address-of operator; it produces a pointer pointing to the referent. In this case, error is an NSError *,it takes an address to it and may modify error through that pointer to indicate the error that occurred.