iphone - requires expression of scalar type?

I have this method on the delegate

- (BOOL) isBook:(int)number {
    if (  ((number >= 0) && (number < 73)) ||
            ((number >= 432) && (number < 2864)) ) { 
        return YES; 
    }

    return NO;
}

then I have this call on the class (yes the class has a delegate protocol declar开发者_如何学运维ed).

if ([delegate isBook:number]) {
  //do stuff
}

I have an error on this IF saying: error: statement requires expression of scalar type ('void' invalid) ??????????

I have tried to do

if ([delegate isBook:numnber] == YES)

but it gives me another error: invalid operands to binary expression ('void' and 'int')

Why is that?

thanks

If your protocol is expressing that method as this:

- (void)isBook:(int)number;

Then that's most likely how you get the error; change it so it returns BOOL like your implementation.