freducer

This package contains an implementation of tomatau's type-to-reducer package, for use with pburtchaell's redux-promise-middleware. If you have absolutely no idea what type-to-reducer does, I really recommend taking a look at that as well - although hopefully this package's API is simple enough will be able to bypass that altogether in many scenarios. However, you will definitely need to understand the use the redux-promise-middleware.

Basic usage

Take the following reducer, written with standard Redux syntax:

const myReducer = (state, action) => {
  switch (action.type) {
    case 'GET_RESOURCE_PENDING':
      return {
        ...state,
        pending: true
      }
    case 'GET_RESOURCE_FULFILLED':
      return {
        ...state,
        success: true,
        data: action.payload
      }
    case 'GET_RESOURCE_REJECTED':
      return {
        ...state,
        error: action.payload
      }
    case 'UPDATE_RESOURCE_PENDING':
      return {
        ...state,
        pending: true
      }
    case 'UPDATE_RESOURCE_FULFILLED':
      return {
        ...state,
        success: true,
        data: action.payload
      }
    case 'UPDATE_RESOURCE_REJECTED':
      return {
        ...state,
        error: action.payload
      }
    default:
      return state
  }
}

Pretty long and messy right? Using a package like typeToReducer we can improve the code a bit by writing something like this:

import typeToReducer from 'type-to-reducer'

const initialState = {
  pending: false,
  success: false,
  error: null,
  data: {}
}

const myReducer = typeToReducer({
  [GET_RESOURCE]: {
    PENDING: {
      ...initialState,
      pending: true
    }
    REJECTED: {
      ...initialState,
      error: payload
    }
    FULFILLED: {
      ...initialState,
      success: true,
      data: payload
    }
  }
  [UPDATE_RESOURCE]: {
    PENDING: {
      ...initialState,
      pending: true
    }
    REJECTED: {
      ...initialState,
      error: payload
    }
    FULFILLED: {
      ...initialState,
      success: true,
      data: payload
    }
  }
}, { initialState })

A bit better right? But still a lot of repeated code... Imagine if you could simplify this to:

import { asyncReducer, asyncMethod } from 'freducer'

const myReducer = asyncReducer({
  [GET_RESOURCE]: asyncMethod()
  [UPDATE_RESOURCE]: asyncMethod()
})

Well now you can (note that we also no longer have to define initialState)!

Default export

full reducer (freducer)

Often, as in the previous example, one part of the store will be affected by multiple actions. However in the most simple situation a reducer will only have a single action, for example UPSERT_RESOURCE. At this level, we once again start repeating code, but not anymore...

Using the asyncReducer & asyncMethod functions above, we might write something like this:

const myReducer = asyncReducer({
  [UPSERT_RESOURCE]: asyncMethod()
})

Using freducer's default export, we can instead write:

const reducer = fullReducer(UPSERT_RESOURCE)

INCREDIBLE!

Options

initialState

If we only require a basic async reducer, we can leave both arguments blank as in the example above. However 2 options are available to customise the reducer. The most common will be initialState as we will quite often want to set a different default value for the data field. This is no problem - simply pass an object containing whatever fields you want to overwrite:

const initialState = { data: [] }

const reducer = asyncReducer({
  [GET_RESOURCE]: asyncMethod({ initialState })
}, initialState)

Note that whatever you object you pass here will be merged (using spread operator) with the default object.

locationFunction

Secondly we are able to tell our reducer to write to nested objects using a locationFunction argument. For example we may wish to do something like this:

const myReducer = typeToReducer({
  [GET_RESOURCE_WITH_ID]: {
    PENDING: {
      ...state,
      [meta.id]: {
        ...initialState,
        pending: true
      }
    }
    REJECTED: {
      ...state,
      [meta.id]: {
        ...initialState,
        error: payload
      }
    }
    FULFILLED: {
      ...state,
      [meta.id]: {
        ...initialState,
        success: true,
        data: payload
      }
    }
  }
}, { initialState })

Instead we can simply write:

const locationFunction = (state, action, internal) => {
  return {
    ...state,
    [action.meta.id]: {
      ...internal
    }
  }
}

const myReducer = asyncReducer({
  [GET_RESOURCE]: asyncMethod({ locationFunction })
})

The arguments state & internal are less confusing than they seem. internal refers to the object you are trying to place in the store i.e. with error, success etc.. And the default setting is to simply place it where the state tree begins. So this function simply describes the steps to get from state i.e. the root of this reducers section of the store, to wherever you want to place the 'internals'.