Question regarding BindingState wrapper

[jkay-kim]

struct SomeFeature: ReducerProtocol {
    struct State: Equatable {
        @BindingState var someText: String = ""
    }
    
    enum Action: BindableAction {
        case binding(BindingAction<State>)
    }
    
    func reduce(into state: inout State, action: Action) -> EffectTask<Action> {
        switch action {
        case .binding(\.someText):
            return .none
            
        case .binding:
            return .none
        }
    }
}

Hello. I am new to TCA.
When I try to bind a TextField from a view to viewStore.$someText, the state of 'someText' is not updated. It remains the initial value "".
I think there is no logic to set the new text value to the someText variable, such as state.someText = newValue.
How can I solve the problem?

Thank you 🙇‍♂️

[mbrandonw]

Hi @jkay-kim, yes something is missing from your code. You should have seen a purple warning in Xcode letting you know that something was wrong when you typed into the text field. Did you not?

To fix this you have to use the BindingReducer. We have an article in the documentation that describes this, but in your case you want this:

struct SomeFeature: ReducerProtocol {
  struct State: Equatable {
    @BindingState var someText: String = ""
  }
  
  enum Action: BindableAction {
    case binding(BindingAction<State>)
  }
  
  var body: some ReducerProtocolOf<Self> {
    BindingReducer()
    
    Reduce { state, action in 
      switch action {
      case .binding(\.someText):
        return .none
          
      case .binding:
        return .none
      }
    }
  }
}

[jkay-kim]

@mbrandonw Thank you for your answer.
I was misunderstanding the concept of Reducer body & Reduce function that Reduce function is required func.
After moving implementation of reduce function to reducer body including BindingReducer() as you suggested, it works like a magic. Thank you!