ComposableSearchable.swift

import SwiftUI
import ComposableArchitecture

struct SearchableState: Equatable {
  var searchText = ""
  var names = ["Oliver", "Emily", "Jessica", "Dan", "Eva"]
  
  var searchResults: [String] {
    if searchText.isEmpty {
      return names
    } else {
      return names.filter { $0.lowercased().contains(searchText.lowercased()) }
    }
  }
  
  var isSearching = false
  
  var sectionTitle: String {
    self.isSearching ? "Searching" : "Not Searching"
  }
}

enum SearchableAction {
  case binding(BindingAction<SearchableState>)
}

struct SearchableEnvironment {}

let searchableReducer = Reducer<SearchableState, SearchableAction, SearchableEnvironment> { _, _, _ in .none }
  .binding(action: /SearchableAction.binding)

struct SearchableView: View {
  let store: Store<SearchableState, SearchableAction>
  
  var body: some View {
    WithViewStore(self.store) { viewStore in
      NavigationView {
        SearchableList(store: self.store)
          .navigationBarTitle("Searchable")
          .searchable(
            text: viewStore.binding(keyPath: \.searchText, send: SearchableAction.binding),
            prompt: "Search names..."
          )
      }
    }
  }
}

struct SearchableList: View {
  let store: Store<SearchableState, SearchableAction>
  
  @Environment(\.isSearching) var isSearching
  
  var body: some View {
    WithViewStore(self.store) { viewStore in
      List {
        Section(viewStore.sectionTitle) {
          ForEach(viewStore.searchResults, id: \.self) { name in
            Text(name)
          }
        }
      }
      .onChange(of: isSearching) { newValue in
        viewStore.send(.binding(.set(\.isSearching, newValue)))
      }
    }
  }
}

struct SearchableView_Previews: PreviewProvider {
  static var previews: some View {
    SearchableView(
      store: Store(
        initialState: .init(),
        reducer: searchableReducer,
        environment: .init()
      )
    )
  }
}