Is it true that once you get approved por citizenship you get sworn on the spot?

[Rick Moranis]

A friend of mine is going for his interview in a month and he wants to know the following once he gets approved to become a citizen, Does he actually have the rights of a citizen or Does he have to wait to be sworn? I understand some centers do the ceremony on the spot. Is it true also that you might have to wait up to a year for the ceremony and therefore to be legally a citizen?