throwing an exception in objective-c/cocoa

Question

What\'s the best way to throw an exception in objective-c/cocoa?

Answer 1

There is no reason not to use exceptions normally in objective C even to signify business rule exceptions. Apple can say use NSError who cares. Obj C has been around a long time and at one time ALL C++ documentation said the same thing. The reason it doesnt matter how expensive throwing and catching an exception is, is the lifetime of an exception is exceedingly short and...its an EXCEPTION to the normal flow. I have never heard anyone say ever in my life, man that exception took a long time to be thrown and caught.

Also, there are people that think that objective C itself is too expensive and code in C or C++ instead. So saying always use NSError is ill-informed and paranoid.

But the question of this thread hasnt yet been answered whats the BEST way to throw an exception. The ways to return NSError are obvious.

So is it: [NSException raise:... @throw [[NSException alloc] initWithName.... or @throw [[MyCustomException... ?

I use the checked/unchecked rule here slightly differently than above.

The real difference between the (using the java metaphor here) checked/unchecked is important --> whether you can recover from the exception. And by recover I mean not just NOT crash.

So I use custom exception classes with @throw for recoverable exceptions, because its likely I will have some app method looking for certain types of failures in multiple @catch blocks. For example if my app is an ATM machine, I would have a @catch block for the "WithdrawalRequestExceedsBalanceException".

I use NSException:raise for runtime exceptions since I have no way to recover from the exception, except to catch it at a higher level and log it. And theres no point in creating a custom class for that.

Anyway thats what I do, but if there's a better, similarly expressive way I would like to know as well. In my own code, since I stopped coding C a hella long time ago I never return an NSError even if I am passed one by an API.