ios4 - Cant able to get phone number from iphone -

currently i'm using following code local device phone number :

nsstring *num = [[nsuserdefaults standarduserdefaults]                  stringforkey:@”sbformattedphonenumber”];  nslog(@”phone number: %@”, num); 

but can't able number, shows null. can 1 guide me how solve problem!!

thanks in advance

there no supported way device's phone number. method (such "sbformattedphonenumber" mentioned in other answers) happens work liable app rejected , liable stop working @ point without notice.

if need phone number, ask user enter it.