UISwipeGestureRecognizer addGestureRecognizer to view in childview error - ios

Question

after some years I tried again to work with XCode to write some little apps for iOS.
My MainViewController contains these lines in viewdidload:
UIStoryboard* overviewStoryboard = [UIStoryboard storyboardWithName:#"MainStoryboard" bundle:nil];
UIViewController *overviewController = [overviewStoryboard instantiateViewControllerWithIdentifier:#"Overview"];
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:overviewController];
...
[self addChildViewController:nav];
[self.view addSubview:nav.view];
[nav didMoveToParentViewController:self];
the Controller behind the Overview contains the whole gesture recognition in view did load:
the property
#property (nonatomic, strong) UISwipeGestureRecognizer *swipeGestureUpDown;
viewdidload:
self.tableView.dataSource = self;
self.tableView.delegate = self;
// gesture recognizer top
self.swipeGestureUpDown = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(swipedScreen)];
self.swipeGestureUpDown.numberOfTouchesRequired = 1;
self.swipeGestureUpDown.direction = (UISwipeGestureRecognizerDirectionUp | UISwipeGestureRecognizerDirectionDown);
[self.view addGestureRecognizer:self.swipeGestureUpDown];
and swipedScreen only an nslog:
- (void)swipedScreen:(UISwipeGestureRecognizer*)gesture
{
NSLog(#"somewhere");
}
THE overviewcontroller contains a tableView with custom cells.
The maincontroller passes this overviewcontroller as rootcontroller to a navigation, which should be slideUp if you swipeUp, and slideIn if you swipeDown. The maincontroller is calling the navigationcontroller with rootcontroller as you've seen above.
Nothing happens, no gesture is recognized, and in some tries it crashes with this message
unrecognized selector sent to instance
does somebody now what to do?

Answer 1

Answer to the question came up in the comments. Just consolidating it here.
There were a few issues.
First:
self.swipeGestureUpDown = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(swipedScreen)];
#selector(swipedScreen) is missing : at end of swipedScreen which makes it unrecognizable as the definition of the function is - (void)swipedScreen:(UISwipeGestureRecognizer*)gesture
Second:
self.swipeGestureUpDown.direction = (UISwipeGestureRecognizerDirectionUp | UISwipeGestureRecognizerDirectionDown);
Having single gesture recognizer for two directions of swipe does not work. For details see this. You will need to have a dedicated gesture recognizer for each direction.
Third:
Most important of all was trying to add Up and Down direction swipes on UITableView which won't work as long as scrolling is enabled in UITableView as it has its own default actions to handle these swipes which prevents it from being handled manually. But if you have very limited content in the table and don't need scrolling, you can set scrollEnabled to false which will make UITableView stop using the gestures and forward the gestures higher up the responder chain. Refer scrollEnabled description here. (UITableView inherits from UIScrollView.)