reducer_magic.js

// Switch
const applicationReducer = (state, action) => {
  switch (action.type) {
    case "FETCH_PACKAGES/START":
    case "FETCH_DEPENDENCIES/START":
      return {
        ...state,
        fetch_count: state.fetch_count + 1
      };

    case "FETCH_PACKAGES/SUCCESS":
    case "FETCH_PACKAGES/FAILED":
    case "FETCH_DEPENDENCIES/SUCCESS":
    case "FETCH_DEPENDENCIES/FAILED":
      return {
        ...state,
        fetch_count: state.fetch_count + 1
      };

    default:
      return state;
  }
};

// My Magic
const applicationReducer = createReducer({
  [oneOf("FETCH_PACKAGES", "FETCH_DEPENDENCIES")]: {
    START(state, action) {
      return {
        ...state,
        fetch_count: state.fetch_count + 1
      };
    },
    [oneOf("FAILED", "SUCCESS")](state, action) {
      return {
        ...state,
        fetch_count: state.fetch_count + 1
      };
    }
  }
});

// My Magic + immer
const applicationReducer = createReducer({
  [oneOf("FETCH_PACKAGES", "FETCH_DEPENDENCIES")]: {
    START(state, action) {
      state.fetch_count++;
    },
    [oneOf("FAILED", "SUCCESS")](state, action) {
      state.fetch_count--;
    }
  }
});