Delegate property with different type in Swift

Question

Ok so we have UIScrollView declaration:

protocol UIScrollViewDelegate: NSObjectProtocol { ... }
class UIScrollView: UIView {
    ...
    weak var delegate: UIScrollViewDelegate?
    ...
}

And then UITableView with delegate variant?

protocol UITableViewDelegate: NSObjectProtocol, UIScrollViewDelegate { ... }
class UITableView: UIScrollView {
    ...
    weak var delegate: UITableViewDelegate?
    ...
}

How Apple did this? When I do my

protocol MyScrollViewSubclassDelegate: NSObjectProtocol, UIScrollViewDelegate { ... }
class MyScrollViewSubclass: UIScrollView {
    ...
    weak var delegate: MyScrollViewSubclassDelegate?
    ...
}

I get Property 'delegate' with type 'MyScrollViewSubclassDelegate?' cannot override a property with type 'UIScrollViewDelegate?'.

Answer 1

I stumbled upon this a few times and the only work-around I found was just calling my property something else like customDelegate or whatever you like.

It would be neat indeed to be able to just call it delegate but hey!

Answer 2

MyScrollViewSubclass has the delegate property of UIScrollView because it's subclass of UIScrollView.

As delegate is already defined by UIScrollView, you cannot define the same property name with a new type.

Change the variable name delegate to myDelegate (or something else) and it should work.