How to obtain the Child.State from the Destination.State property?

[idelfonsog2]

if I have the following:

struct Destination: ReducerProtocol {
        enum State: Equatable {
            case one(OneFeature.State)
            case two(TwoFeature.State)
        }
}

how can I case unwrap the OneFeature.State in my ParentFeature reducer?

I have been trying:

...
   if case let Destination.State.one(oneState) = state.destination {
..

but the error keeps statingEnum case 'one' is not a member of type 'ParentFeature.Destination.State?'

[mbrandonw]

Does this work:

if case let .some(.one(oneState)) = state.destination

? I would expect optional promotion to just work, but maybe it needs some help.

[dikasetiadi]

maybe you can tried using CasePath like this:

extension CasePath where Root == Destination.State, Value == OneFeature.State {
    internal static let oneData = CasePath(
        embed: { Destination.State.one },
        extract: {
            guard case let .one(state) = $0 else { return nil }
            return state
        }
    )
}

and on the reduce func you can use it like this

...
   if let oneState = CasePath.oneData.extract(from: state.destination) {
        /// your logic code below
   }
..