Optional Store when scoping on optional state

[fbp93]

I need to perform a scope where the state is optional and being able to transform a Store<State?, Action> into Store<State, Action>?.
To avoid some manual unwrap, I tried to add some syntactic sugar, here is how I did it:

extension Store {
  public func optional<Wrapped: Equatable>() -> Store<Wrapped, Action>? where Wrapped? == State {
      var result: Store<Wrapped, Action>?
      _ = self.publisherScope(state: { $0.compactMap { $0 } }).sink(receiveValue: {
        result = $0
      })
      return result
  }
}

// Usage:
self.store.scope(state: \.state, action: AppAction.action).optional()

The problem is that solution is not safe and the publisherScope is deprecated.

What about adding a safe API to retrieve an optional store from an optional state?

[iampatbrown]

@fbp93 Is this for UIKit? What do you mean by unsafe?

Here is an alternate version of your extension using .ifLet:

extension Store {
  public func unwrap<Wrapped>() -> Store<Wrapped, Action>? where State == Wrapped? {
    var unwrapped: Store<Wrapped, Action>?
    _ = self.ifLet { unwrapped = $0 }
    return unwrapped
  }
}

[stephencelis]

Hi @fbp93! This is precisely what Store.ifLet, which unwraps a store on optional state in the trailing closure.

@iampatbrown's unwrap could be used in a synchronous context, but might be dangerous to use over time, so prefer ifLet if you can.

I'm going to convert this to a discussion since it's a question about library use and we like to keep the issues section focussed on bugs.

[iampatbrown]

@stephencelis agreed. I probably should have mentioned that too :P

[fbp93]

Thanks a lot!