Sending isEqual: to nil always returns NO

Question

If you send isEqual: to an object that happens to be nil, you always get NO back.

Is this the expected behavior? To be a feature instead of a bug, I would expect i

Answer 1

This is expected behaviour from Objective-C. This basically means that doing this

if ([nil isEqual:nil]) { ... }

evaluates to NO. Even though it doesn't make sense, when looking at it - and even though it's annoying - being able to send messages to nil is actually one of the really cool things about Objective-C. Saves you a lot of code sometimes.

My solution is to define this macro somewhere handy

#define IsEqual(x,y) ((x && [x isEqual:y]) || (!x && !y))

So when I need to test if two objects are equal:

if (IsEqual(obj1, obj2)) { ... }

or not equal:

if (!IsEqual(obj1, obj2)) { ... }

Hope this helps.