Swift override protocol methods in subclasses

Question

I have a base class that implements an extension that conforms to the protocol as shown below:

protocol OptionsDelegate { func handleSortAndFilter(opt: Options) } extension BaseViewController: OptionsDelegate { func handleSortAndFilter(opt: Options) { print("Base class implementation") } } 

I have a subclass of "InspirationsViewController" that inherits from BaseViewController. And I redefine the protocol method in the extension, as shown below:

 extension InspirationsViewController { override func handleSortAndFilter(opt: Options) { print("Inside inspirations") } } 

I get an error when I redefine the function "handleSortAndFilter" in a subclass extension: "Decryption in extensions cannot yet override"

But I do not see a similar problem when I implemented the UITableView and delegation data methods.

How to avoid this error?

Answer 1

Use the protocol extension with the where clause. He works.

 class BaseViewController: UIViewController { } extension OptionsDelegate where Self: BaseViewController { func handleSortAndFilter(opt: Options) { print("Base class implementation") } } extension BaseViewController: OptionsDelegate { } class InsipartionsViewController: BaseViewController { } extension OptionsDelegate where Self: InsipartionsViewController { func handleSortAndFilter(opt: Options) { print("Inspirations class implementation") } } 

Answer 2

As far as I know, you cannot override methods in extensions. Extensions can only perform the following actions: "Extensions in Swift can:

• Add properties of computed instances and properties of computed type
• Define instance methods and type methods
• Provide new initializers
• Define Indexes
• Define and use new nested types
• Make existing type conform to protocol

Excerpt from: Apple Inc. "Fast programming language (Swift 3.0.1)."