@interface Foo : NSObject
{
   id bar;
}

@property (readwrite, retain) bar;

@end

@implementaion Foo

@synthesize bar;

- (id)init
{
   if(self = [super init])
   {
       Bar *b = [[Bar alloc] init];
       self.bar = b;
       [b release];
   }
   return self;
}

- (void)dealloc
{
   if(self.bar)
   {
       [self.bar release];
       self.bar = nil;
   }
   [super dealloc];
}

@end

self.bar

if(bar) ...