gistfile1.m

// DNSSDService implements -isEqual: based on a comparison of the domain, type and name, and  
// it implements -hash correspondingly.  This allows you to use DNSSDService objects in sets, 
// as dictionary keys, and so on.
//
// IMPORTANT: This uses case-sensitive comparison.  In general DNS is case insensitive. 
// DNS-SD will always pass you services with a consistent case, so using case sensitive 
// comparison here is not a problem.  You might run into problems, however, if you do 
// odd things like manually create a DNSSDService with the domain set to "LOCAL." instead 
// of "local.".
// 
// DNSSDService also implements NSCopying.  When you copy a service, the copy has the same 
// domain, type and name as the original.  However, the copy does not bring across any of 
// the resolution state.  Specifically:
//
// o If the original was resolving, the copy is not.
//
// o If the original had successfully resolved (and thus has resolvedHost and resolvedPort set), 
//   these results are not present in the copy.
//
// However, because the domain, type and name are copied, and these are the only things 
// considered by -isEqual: and -hash, DNSSDService can be used as a dictionary key.

- (BOOL)isEqual:(id)object
{
    DNSSDService *other;

    // Boilerplate stuff.
    if (object == self) {
        return YES;
    }
    if (![object isKindOfClass:[self class]] ) {
        return NO;
    }
    
    // Compare the domain, type and name.
    other = (DNSSDService *)object;
    return [self.domain isEqualToString:other.domain] && [self.type isEqualToString:other.type] && [self.name isEqualToString:other.name];
}