ios - NSUserDefaults deleting keys when close the app -

i need delete keys when application close. should do?

delete keys nsuserdefaults using following code

[[nsuserdefaults standarduserdefaults] removeobjectforkey:@"yourkey"]; 

in applicationdelegate method following state meaning "close app":

- (void)applicationwillresignactive:(uiapplication *)application - (void)applicationdidenterbackground:(uiapplication *)application - (void)applicationwillterminate:(uiapplication *)application