RE: Method not seeing array as array
RE: Method not seeing array as array
- Subject: RE: Method not seeing array as array
- From: Jeff Laing <email@hidden>
- Date: Fri, 4 Feb 2005 14:41:13 +1100
> > The problem with "if (!self)" is that you're assuming that
> nil is equal to zero.
(snip)
No, thats not the problem.
> /usr/include/objc/objc.h. lines 51-57:
> #ifndef nil
> #define nil 0 /* id of Nil instance */
> #endif
>
> As for documentation, according to the objective-C language overview
>
> "The keyword nil is defined as a null object, an id with a value of 0.
Ok, there's a bug for you then. The above header does *not* define nil as
"an id with ..." - instead, its "an integer with ..."
If you implement to the word of the spec, you'd have
#ifndef nil
#define nil ((id)0)
#endif
which strict type-checking compilers may well barf on since ! is not a
defined operation for pointer types. Or is it?
I've seen C++ compilers that definitely reject this sort of thing, but some
skate along on the lazy assumptions that says that the literal 0 is
type-compatible with any pointer, and they define !x as ( x != 0 ).
Sure, Objective-C is not C++, but then again, someone might pick up your
code and try to ram it through Objective-C++ which may well have to adhere
to stricter language specs.
Having said all that, I prefer the (!ptr) syntax but I recognise that its a
lot easier to overlook in a page full of text, and *try* to use (ptr == nil)
wherever I can.
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