How to create a new container type to wrap a function like ( closure -> void) in ios swift?

Question

I have a situation where I have create a container which wraps a closure. This closure can be Result enum which has success and failure case.

Create a new container type EventResult<U, E: Error> that wraps a function like ((Result<U,E>) -> Void) -> Void and notifies you in case of success or failure.