Overriding delegate property of UIScrollView in Swift (like UICollectionView does)

Question

UIScrollView has a delegate property which conforms to UIScrollViewDelegate

protocol UIScrollViewDelegate : NSObjectProtocol {
    //...
}
class UIScrollView : U         


        

Answer 1

Here is a solution for changing the type of the overriding properties in Swift. It is especially useful when you need to extend protocols of delegates.

@objc protocol ExtendedUIScrollViewDelegate: UIScrollViewDelegate {
     func someNewFunction()
}

class CustomScrollView: UIScrollView {

    weak var delegateInterceptor: ExtendedScrollViewDelegate?
    override var delegate: UIScrollViewDelegate! {
        didSet {
            if let newValue = delegate {
                let castedDelegate = unsafeBitCast(delegate, ExtendedScrollViewDelegate.self)
                delegateInterceptor = castedDelegate
            }
            else {
                delegateInterceptor = nil
            }
        }
    }
}

This works as tested with Swift version 1.2. I hope it helps.