ios - Difference in ViewController pushing -

i'm doing cs193p stanford course tutorials , apple ios dev tutorials, , there's difference between how push viewcontroller screen

apple this:

 uinavigationcontroller *anavigationcontroller = [[uinavigationcontroller alloc] initwithrootviewcontroller:rootviewcontroller];      self.navigationcontroller = anavigationcontroller; 

stanford suggests doing this:

navigationcontroller = [[uinavigationcontroller alloc] init]; [self.navigationcontroller pushviewcontroller:rootviewcontroller animated:no]; 

how different?

ps: btw, apple's method work , stanford 1 doesn't display , don't know why.

i think using pushviewcontroller:animated method going add controller @ top of stack of controllers (push new view controller on stack).

in second method not initializing navigationcontroller.