gistfile1.txt

import SwiftUI

final class Store<Value, Action>: ObservableObject {
    let reducer: (inout Value, Action) -> Void
    @Published private(set) var value: Value
    
    init(initialValue: Value, reducer: @escaping (inout Value, Action) -> Void) {
        self.reducer = reducer
        self.value = initialValue
    }
    
    func send(_ action: Action) {
        self.reducer(&self.value, action)
    }

}

extension Store {
  public func send<LocalValue>(
    _ action: @escaping (LocalValue) -> Action,
    binding keyPath: KeyPath<Value, LocalValue>
  ) -> Binding<LocalValue> {
    Binding(
      get: { self.value[keyPath: keyPath] },
      set: { self.send(action($0)) }
    )
  }
}

struct AppState { var val = "42" }
enum AppAction { case updateVal(String) }

func reducer(state: inout AppState, action: AppAction) {
    switch action {
    case let .updateVal(val): state.val = val
    }
    
    print(state)
}

let store: Store<AppState, AppAction> = Store(initialValue: AppState(), reducer: reducer)

struct Test: View {
    
    @State var val: String = ""
    
    var body: some View {
        Picker.init("pick",
                    selection: store.send(
                        { newVal in .updateVal(newVal) },
                        binding: \.self.val)
            ){
            Text("bar").tag(1)
            Text("baz").tag(2)
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View { Test() }
}