dispatchOncePersistent.h

static inline void dispatchOncePersistent(NSString *prefsKey, void (^aBlock)())
{
    if (![[NSUserDefaults standardUserDefaults] boolForKey:prefsKey]) {
        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:prefsKey];
        [[NSUserDefaults standardUserDefaults] synchronize];

        aBlock();
    }
}

/*
            dispatchOncePersistent(@"show instructions for friend requests", ^{
                [SVProgressHUD showSuccessWithStatus:@"Select a friend to send them a friend request"];
            });
*/