@FocusState: focusedField binding not triggering the binding action when the focusedField is set from the Reducer

[pdrcabrod]

Hello

First of all, congratulations on the great work you have accomplished with TCA.

I have a question. I have been playing a bit with the CaseStudies and I stumbled across a situation I do not know if it is expected or not.

In the 01-GettingStarted-FocusState case study, if I add a new handler for the binding action

case .binding(\.focusedField):
          print("binding focusedField")
          return .none

The log will be only printed if the focusedField is set via tapping on the SwiftUI´s TextField. When the focusedField is set from the Reducer, for example if we tap in the SignIn button and we have not provided a username, the log is not printed.

Is it expected?

I can think of a real world scenario in which something like this would be useful. ie, if we have to customize a complex custom TextField when it gains focus. How could we handle that in the binding is not being triggered?

Thank you so much in advance

[mbrandonw]

Hi @pdrcabrod, yeah this is to be expected. If the focus changes directly in a reducer from some other action:

case .buttonTapped:
  state.focusedField = .title

…then the .binding action can't possibly be destructured in the switch. After all, a .binding action wasn't sent, the .buttonTapped action was sent.

If you just want to listen for any changes to focusField you can use the onChange reducer operator:

CombineReducers {
  BindingReducer()
  Reduce { state, action in … }
}
.onChange(of: \.focusField) { … }

You can look at the docs for onChange for more information of how to use it.