How to fix "Chaining onto properties of binding state is deprecated" warnings?

[darrarski]

I've recently updated ComposableArchitecture from v0.54.1 to v0.56.0 and noticed the following warnings appearing across my code:

'subscript(dynamicMember:)' is deprecated: Chaining onto properties of binding state is deprecated. Instead of pattern matching into a deeper property of binding state, use 'ReducerProtocol.onChange(of:)' to detect changes to nested properties of binding state. Instead of using 'viewStore.binding(.$nested.property)', use dynamic member lookup ('viewStore.$nested.property').

At first sight, it's hard to guess which part of my code triggers it, because Xcode 14.3.1 (14E300c) provides just the file, without an exact line number.

After a brief investigation, I think the problem lays in the following code of my reducers:

Reduce { state, action in
  // ...
  case .binding(\.$query.dateRange): // <-- this line triggers the warning
    return .task { .loadInfo }
  // ...
}

and in my SwiftUI views:

struct DashboardFiltersView: View {
  let store: StoreOf<DashboardComponent>

  struct ViewState: Equatable {
    init(state: DashboardComponent.State) {
      query = state.query
      isLoading = state.isLoading
    }

    var query: DashboardInfoProvider.Query
    var isLoading: Bool
  }

  public var body: some View {
    WithViewStore(store, observe: ViewState.init) { viewStore in
      DayRangeFormView(
        range: viewStore.binding(
          get: \.query.dateRange,
          send: { DashboardComponent.Action.set(\.$query.dateRange, $0) } // <-- this line triggers the warning (probably)
        )
      )
      .disabled(viewStore.isLoading)
    }
  }
}

Despite the hints to use ReducerProtocol.onChange(of:) and dynamic member lookup, I'm not sure how the warnings can be fixed.

Will appreciate support from this amazing community :-)

[darrarski]

I think I found a way to silence the warnings that appeared in my reducers like this:

Before:

BindingReducer()

Reduce { state, action in
  // ...
  case .binding(\.$query.dateRange): // <-- this line triggers the warning
    return .task { .loadInfo }
  // ...
}

After:

BindingReducer()
  .onChange(of: \.query.dateRange) { _, _ in
    Reduce { _, _ in 
      return .task { .loadInfo } 
    }
  }

Reduce { state, action in
  // ...
}

I'm not sure if this is the correct way though. It adds tons of boilerplate code, especially in places where I had multiple actions in pattern matching:

BindingReducer()

Reduce { state, action in
  // ...
  case .binding(\.$query.dateRange),
    .binding(\.$query.someProperty1),
    .binding(\.$query.someProperty2),
    .binding(\.$query.someProperty3):
    return .task { .loadInfo }
  // ...
}

becomes:

BindingReducer()
  .onChange(of: \.query.dateRange) { _, _ in
    Reduce { _, _ in 
      return .task { .loadInfo } 
    }
  }
  .onChange(of: \.query.someProperty1) { _, _ in
    Reduce { _, _ in 
      return .task { .loadInfo } 
    }
  }
  .onChange(of: \.query.someProperty2) { _, _ in
    Reduce { _, _ in 
      return .task { .loadInfo } 
    }
  }
  .onChange(of: \.query.someProperty3) { _, _ in
    Reduce { _, _ in 
      return .task { .loadInfo } 
    }
  }

Reduce { state, action in
  // ...
}

I still have no idea how to fix the warnings in my SwiftUI views.

[saroar]

Brandon Williams
3 days ago
Also you cannot use .send(.set(.$vCard.contact.firstName, …)). that should produce a deprecation warning. you must send the entire vCard in the action: .send(.set(.$vCard, …)).

[mbrandonw]

We detailed all of these changes in this discussion, but the tldr is that while the previous syntax seemed great, there were a lot of gotchas that you can fall into, and people often did. So we had to change things.

Also, FWIW you should be able to simplify your chain of onChanges with something like this:

BindingReducer()
  .onChange(
    of: { ($0.query.dateRange, $0.query.someProperty1, $0.query.someProperty2, $0.query.someProperty3) },
    removeDuplicates: ==
  ) { _, _ in
    Reduce { _, _ in 
      return .task { .loadInfo } 
    }
  }

However, it looks like we are missing the removeDuplicates variation of onChange and so it may be worth adding that. Too bad tuples aren't equatable in Swift :/

[saroar]

[JOyo246]

Our team is seeing the warning in many files across our app, despite only using binding chaining in 2 views. Some of the warnings are in files that don't even import TCA. Is this expected?

[mbrandonw]

Just sounds like a bug in Xcode. Often Xcode will put test failures, compile errors and deprecation warnings on the wrong line or on an entire file instead of the line. Have you tried fixing the warnings to see if that helps?

[salavert]

@JOyo246 I had the same problem and found this is due to batch mode, you can revert to the previous single file strategy with custom Build Setting SWIFT_ENABLE_BATCH_MODE = NO and it will pinpoint to the problematic file, or at least that's what solved my problem.