Manually scrolling UIScrollView (iOS/Swift)

Recently while working with one of my libraries, I realized that I wanted to manually scroll UIScrollView in any direction. (Viz. Top, Right, Bottom, Left). It took me quite time to find examples online. But I take this moment to compile them together.

Since Swift is a hot word in iOS kingdom, I will make a UIScrollView extension with Swift which can be used to manually scroll the view in any direction.

In order to take advantage of Swift constructs, I have used enums and encapsulated as much logic possible inside enum since Swift enables us to include methods inside enum.

Let's start with enum defining 4 directions

enum ScrollDirection {
    case Top
    case Right
    case Bottom
    case Left
}

Now let's include additional methods to this enum which will take UIScrollView instance as a parameter and depending on the value of self, it will return appropriate contentOffset

enum ScrollDirection {
    case Top
    case Right
    case Bottom
    case Left
    
    func contentOffsetWith(scrollView: UIScrollView) -> CGPoint {
        var contentOffset = CGPoint.zero
        switch self {
            case .Top:
                contentOffset = CGPoint(x: 0, y: -scrollView.contentInset.top)
            case .Right:
                contentOffset = CGPoint(x: scrollView.contentSize.width - scrollView.bounds.size.width, y: 0)
            case .Bottom:
                contentOffset = CGPoint(x: 0, y: scrollView.contentSize.height - scrollView.bounds.size.height)
            case .Left:
                contentOffset = CGPoint(x: -scrollView.contentInset.left, y: 0)
        }
        return contentOffset
    }
}

We are almost there. Now add an extension to UIScrollView which will take parameter direction of type ScrollDirection and optional parameter which will indicate if we want scrolling action to be animated or not.

extension UIScrollView {
    func scrollTo(direction: ScrollDirection, animated: Bool = true) {
        self.setContentOffset(direction.contentOffsetWith(self), animated: animated)
    }
}

So for example, if you want to manually scroll any UIScrollView instance, you will just utilize the above code as follows,

let myScrollView = UIScrollView()

// With animation - Animation is enabled by default
myScrollView.scrollTo(.Top/.Right/.Bottom/.Left)

// Without animation
myScrollView.scrollTo(.Top/.Right/.Bottom/.Left, animated: false)

Hope this will help you in any of your side projects. The beauty of this approach is that we managed to move code which calculates content offset inside enum construct - Making UIScrollView extension easier to manage

Jayesh Kawli

I am a web and mobile developer working at Wayfair in Boston, MA. I come to learn so many things during course of life and I write about things which helped me and feel like they can help others too.

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