combine-your-reducers-1.js

const reducerLoading = (actionInit, actionSuccess, actionError) => (
  state = false,
  action,
) => {
  switch (action.type) {
    case actionInit.type:
      return true
    case actionSuccess.type:
      return false
    case actionError.type:
      return false
  }
}

class CatsGetInit extends ActionStandard {}
class CatsGetSuccess extends ActionStandard {}
class CatsGetError extends ActionStandard {}

const reducerCatsData = (state = undefined, action) => {
  switch (action.type) {
    case CatsGetSuccess.type:
      return action.payload
    default:
      return state
  }
}
const reducerCatsError = (state = undefined, action) => {
  switch (action.type) {
    case CatsGetError.type:
      return action.payload
    default:
      return state
  }
}

const reducerCats = combineReducers({
  data: reducerCatsData,
  loading: reducerLoading(CatsGetInit, CatsGetSuccess, CatsGetError),
  error: reducerCatsError,
})