Adding an interface to a Dart extention method

Question

Is it possible to add an interface to a Dart extension? In Swift you can do this:

protocol MyProtocol {
  associatedtype Item
  mutating func nextItem() -> Item?
}

extension MyClass: MyProtocol {

  public typealias Item = T

  public mutating func nextItem() -> T? {
    // ...
  }
}

How do you do that in Dart? It seems this is not possible:

extension MyClassExtension on MyClass implements MyInterface {
  T? nextItem() {
    // ...
  }
}

user_3681880 · Answer

It isn't possible to add an interface to a Dart extension. See the discussion here:

You have to manually add the methods from the interface as you would a normal extension method:

extension MyClassExtension on MyClass {
  T? nextItem() {
    // ...
  }
}

Adding an interface to a Dart extention method

1 Answers