Question from Program 10.3

[bpcookson]

I was just typing this program out and had a question:

Are the following two statements equal?

if ( days != 0 )
-and-
if ( days )

Are there any cases where this logic will fail?  Is there a practical reason to use the first statement beyond readability?

Thanks for any input!
Brian

[skochan]

Yes, they're equal.  The logic can fail if a method is defined to return a BOOL value and returns a nonzero value to indicate success instead of the value YES.  That can lead to trouble if a statement like this is written:

Code: (Objective-C)

 
if ( [myObject testCondition] == YES )
   ...

That is, a BOOL method should return either YES or NO.   You can assume all Apple methods will return either of these two values, but be wary of third-party code that may not.

Cheers,

Steve