Adding a callback to a Redux Reducer

Question

Would there be anything wrong/anti-pattern-ish (in terms of 'thinking-in-react/redux') in added a callback to the action.data passed into an action?

// reducer
ACTION_FOR_REDUCER() {
  var x = 123
  if ( action.data.callback ) action.data.callback( x )
  return {
    something: action.data.somedata
  }
},

Then accessing that data later in the App when the action is called (in an container perhaps)

// later in the app
this.props.dispatch(changeSomething({
  somedata: somedata,
  callback: (x) => { console.log(x) }
}))    

Answer 1

The idea is not wrong, the implementation is.

Instead of adding a callback, return a promise from the action (you will need redux-thunk middleware or some similar alternative).

Then you can simply do:

dispatch(myAction).then(callback);

Of course, you can also simply dispatch another action in your callback, which usually end up being one compound action.

const myAction = ...
const callbackAction = ...

const compoundAction = () => dispatch => {
     dispatch(myAction())
         .then(() => dispatch(callbackAction()));
};