redux-thunk-routine-part-7.ts

// Use type guards
const reducer = (state: State = initState, action: Action<any>): State => {
  // isSuccessAction is a type guard
  if (fetchDataRoutine.isSuccessAction(action)) {
    // action is typed as Action<DataType>, so payload is DataType
    const payload = action.payload;
    // ...
  }

  // isFailureAction is a type guard
  if (fetchDataRoutine.isFailureAction(action)) {
    // action is typed as Action<Error>, so error is Error
    const error = action.payload;
    // ...
  }
};

// Use getter functions directly
const reducer = (state: State = initState, action: Action<any>): State => {
  switch (action.type) {
    case fetchDataRoutine.SUCCESS: {
      // payload is typed as Action<DataType>
      const payload = fetchDataRoutine.getSuccessPayload(action);
      // ...
      break;
    }
    case fetchDataRoutine.FAILURE: {
      // error is typed as Error
      const error = fetchDataRoutine.getFailurePayload(action);
      // ...
      break;
    }
  }
};