On 21 Aug 2008, at 09:06, Jules Colding wrote:
On 21/08/2008, at 01.56, John C. Randolph wrote:
On Aug 20, 2008, at 4:15 PM, Torsten Curdt wrote:
There was a common perception that NULL is not really the same as
nil. But seems like in the end it really is (void*)0.
They differ in type, not in value.
"NULL" is (void *) 0.
"nil" is (id) 0.
"Nil" is (Class) 0.
Personally, I prefer "if (!foo)" over "if (foo == nil)", because
the latter has the hazard of a typo that compiles. You can lose a
fair bit of time staring at "if (foo = nil)" before you spot the
mistake.
Which is why you should always write "if (nil == foo)".
Just to add my 2 cents to this discussion, I think there's something
which hasn't been brought up (and I guess isn't often brought up by C
programmers).
One of the two options doesn't make sense here.
Because of C's weak type system ! works on almost anything you throw
at it. However, it is a *boolean* operator. Boolean negating a
pointer is a hack that by happy coincidence works. On the other hand,
nil == foo is type safe, and makes semantic sense.
For that simple reason, I'd go for nil == foo every time.
Bob
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