On Sep 8, 2010, at 12:40 PM, Chris Tracewell wrote:
> On Sep 8, 2010, at 12:02 PM, cocoa-dev-requ...@lists.apple.com wrote:
>> It's not YES that's being "returned as" -256, but NO. (The answer is NO in
>> all 3 cases.) -256 is 0xFFFFFF00, so you can see that NO (i.e. (signed char)
>> 0) is being correctly returned in the low order byte, with trash in the high
>> order bytes that's left over from earlier code.
>>
>> So, the problem is not your 'isLessThanZero' method, but the calling code,
>> which is treating the returned value as an int (or something). Presumably
>> the calling code was compiled with an incompatible declaration of your
>> method, or of the BOOL type.
>
> Thanks Quincey, your suggestion got me looking at the calling model and I got
> it working by first assigning the result as a BOOL rather than just using the
> result inside of an if logic statement like so...
>
>
> // ========== Did NOT Work =========//
>
> if ([theDecimalNumber isLessThanZero])
> {
> ... do something
> }
>
> // ========== DID Work =========//
>
> BOOL theResult = [theDecimalNumber isLessThanZero];
> if (theResult)
> {
> ... do something
> }
>
> I must admit that I do not understand why this is so. I can for example use
> if ([someButton isEnabled]) and it returns a BOOL and the if statement works
> fine. If you have any pointers or docs that explains this further I would
> really appreciate it as right now I feel scared about how I have been
> evaluating BOOL's returned in all of my own custom methods.
I bet you have a compiler warning at this call site that says "warning:
'NSDecimalNumber' may not respond to '-isLessThanZero'". That means the
compiler can't see the method declaration for -isLessThanZero at the call site.
In that case, the compiler guesses that the method returns `int`, which is
wrong and will cause incorrect handling of the BOOL value on some architectures.
You need to (1) put your category's @interface in a header file, and (2) import
that header file here.
--
Greg Parker gpar...@apple.com Runtime Wrangler
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