Consider the following code:

enum {
kSomeConstant = 0×0100
};

BOOL test = ( 256 & kSomeConstant ) ;
if ( test ) NSLog(@”BOOL passed”);
if ( ( 256 & kSomeConstant ) ) NSLog(@”int passed”) ;

Only the second NSLog will be executed !.

This is because ‘test’ is actually a char type that can not hold the result of the operation, which is truncated to the least significant byte.

So always, ever (did I say at all times?) use *only* results of boolean operators to assign to BOOLs.

The solution for the code above is to change the test assignment by

BOOL test = ( 256 & kSomeConstant ) != 0 ;

Joan Lluch-Zorrilla.

These are exactly equivalent to your complicated question mark constructions. For example:

bool b = 3.141592654;
will set b to true. Conversion of anything to bool will set it to true if the original was not zero, and to false otherwise. No need to use “? true: false” because that’s what a conversion to bool does by definition.

In the other direction, a bool will always be converted to 0 or 1, which corresponds to NO and YES in the BOOL type, so no worries there, either.

An “if” condition is also implicitly converted to bool, so the same applies there.

The only thing you should avoid, is explicitly comparing to YES.

char* cp = some_address;
if (cp) {
// do something if cp != 0
}

if (!cp) {
// do something if cp == 0
}

So, the magic is in the ! operator. Given:

! value

the result is of type int and is the “logical negation” of the value:

0 if value is nonzero;
1 if value is 0.

You can also say that the expression:

! value

is equivalent to:

(0 == value)

Notice that this explicitly avoids comparing with YES (or 1), which was the main point of my original note.

HTH!

example:
myBOOL = !myBOOL;
newBOOL = !myBOOL;

and so on.

can i pass a message to a method with !myBOOL?