How to get UIScrollView vertical direction in Swift?

Question

How can I get the scroll/swipe direction for up/down in a VC?

I want to add a UIScrollView or something else in my VC that can see if the user swipes/scrolls up or d

Answer 1

I have tried every single response in this thread but none of them could provide a proper solution for a tableView with bounce enabled. So I just used parts of solutions along with some all-time classic boolean flag solution.

1) So, first of all you could use an enum for the scrollDirection:

enum ScrollDirection {
    case up, down
}

2) Set 3 new private vars to help us store lastOffset, scrollDirection and a flag to enable/disable the scroll direction calculation (helps us ignore the bounce effect of tableView) which you will use later:

private var shouldCalculateScrollDirection = false
private var lastContentOffset: CGFloat = 0
private var scrollDirection: ScrollDirection = .up

3) In the scrollViewDidScroll add the following:

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    // The current offset
    let offset = scrollView.contentOffset.y

    // Determine the scolling direction
    if lastContentOffset > offset && shouldCalculateScrollDirection {
        scrollDirection = .down
    }
    else if lastContentOffset < offset && shouldCalculateScrollDirection {
        scrollDirection = .up
    }

    // This needs to be in the last line
    lastContentOffset = offset
}

4) If you have not implemented scrollViewDidEndDragging implement it and add these lines of code inside it:

func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
    guard !decelerate else { return }
    shouldCalculateScrollDirection = false
}

5) If you have not implemented scrollViewWillBeginDecelerating implement it and add this line of code inside it:

func scrollViewWillBeginDecelerating(_ scrollView: UIScrollView) {
    shouldCalculateScrollDirection = false
}

6) Finally, If you have not implemented scrollViewWillBeginDragging implement it and add this line of code inside it:

func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {    
    shouldCalculateScrollDirection = true
}

And if you followed all the steps above you are good to go!

You could go to wherever you want to use the direction and simply write:

switch scrollDirection {
case .up:
    // Do something for scollDirection up
case .down:
    // Do something for scollDirection down
}