Redux Msg

npm i redux-msg

small set of functions to help DRY redux code:

import {
  // helpers for regular redux
  createReducer,
  createSelector,
  createState,

  // special actions called "messages" for advanced code DRYness
  createMessage,
  createMessagesReducer,
  mergeReducers
} from 'redux-msg';

928 bytes in total (gzipped), 0 dependencies, 100% satisfaction

usage examples in this repo

Motivation

Redux is great but applications written using it tend to attract boilerplate code.

Not much is needed to avoid this: only 3 tiny helper functions for starters, or additional 3 (also tiny) functions if you can handle a little convention.

Convention

your redux-aware components should have:

• NAME - string a unique name of component. easily changeable when needed
• MODEL - object the shape of state
• that's it

that's no magic, just:

export const NAME = 'my awesome unique name'
export const MODEL = { woodoo: true, greeting: 'Howdy', randomNumber: 4 }

this convention is helpful even without any of the helper functions suggested here.

API

all 6 exported functions are explained below starting from simplest

createReducer

const { createReducer } = require('redux-msg')

if you code reducers with switches or ifs, this function is for you.

Usage

const { createReducer } = require('redux-msg');
const reducer = createReducer(MODEL)(reducers)`

where:

• MODEL is an object of redux state
• reducers is an object where:
  • key is action type (e.g. COUNTER_INCREASE)
  • value is a reducer function of signature (state, action) => state.

so instead of this:

const reducer = (state, action) => {
  switch(action.type) {
    'increase':
      return { ...state, count: state.count + 1 }
  }
}

you can do this:

const MODEL = { count: 0 }
const reducer = createReducer(MODEL)({
  increase: state => ({...state, count: state + 1})
})

Return Value

createReducer(MODEL)(reducers) returns yet another reducer with signature (state, action) => state. This means that it can be used with other redux tools with no problem.

Example

import { createReducer } from 'redux-msg';

export const MODEL = {
  count: 0
};

// reducer created with `createReducer`
export const reducer = createReducer(MODEL)({
  increase: state => ({ ...state, count: state.count + 1 }),
  setCount: (state, action) => ({ ...state, count: action.count })
});

// ... later

dispatch({ type: 'increase' });
// state is now { count: 1 }
dispatch({ type: 'setCount', count: 10 });
// state is now { count: 10 }

createSelector

const { createSelector } = require('redux-msg')

when you have state, you want to be able to read it easily. easily means from anywhere and always the same way.

let's consider bad approach for a moment.

imagine your store.getState() returns:

{
  counterComponent: {
    count: 0
  }
}

you can create function

const selectCount = state => state.counterComponent.count;

then call it somewhere else

selectCount(store.getState()) // <= 0

however, this doesn't scale well: you need such function for each model property and it also needs to know full path to reach count.

by following simple convention to name your components, you can automatically create such select functions with createSelector without the need to know path to properties.

createSelector(NAME)(MODEL) where:

• NAME is a string labeling your component. This should also be part of combineReducers():

import counterLogic from 'components/counter/logic';
import todoLogic from 'components/todo/logic';

combineReducers({
  [counterLogic.NAME]: counterLogic.reducer,
  [todoLogic.NAME]: todoLogic.reducer
});

a NAME defined once for each redux state section is also useful for other helper functions in this library.

• MODEL is an object of redux state

Return Value

object with keys that are the same as in given MODEL. values are functions of signature state => any, where state is store.getState() and any is whatever type that slice of state is.

For example:

logic.js:

const NAME = 'counterComponent';
const MODEL = {
  count: 0,
  message: 'hello there!'
};

export const select = createSelector(NAME)(MODEL);

assert.deepEqual(Object.keys(selectors), Object.keys(MODEL)) // just to illustrate that both have same keys

console.log(select.count(store.getState())) // <= 0
console.log(select.message(store.getState())) // <= 'hello there!'

this fits really well with react-redux mapStateToProps:

component.js:

import { select } from './logic';

const mapStateToProps = state => ({
  count: select.count(state)
});

Example

import { createSelector } from 'redux-msg';

export const NAME = 'counterComponent';

export const MODEL = {
  count: 0
};

export const selector = createSelector(NAME)(MODEL);

it can be combined with other selectors easily:

export const selectors = {
  ...createSelector(NAME)(MODEL),
  myOtherSelector: state => state[NAME].specialItem
}

createState

const { createState } = require('redux-msg')

helper to create a slice of global state for specific component.

can be used as a state "factory", to hydrate createStore when loading component dynamically or during server side rendering.

can also be used as utility in tests.

Usage

const initState = createState(NAME)(MODEL) where:

• NAME is a string labeling your component. This should also be part of combineReducers(). See createSelector for more details
• MODEL is an object of redux state

Return Value

a function with signature object -> { [NAME]: { ...MODEL, object } }. That's pretty much the actual implementation.

createState(NAME)(MODEL) returns function that accepts object and returns state. The returned state has key name and its value is shallowly merged MODEL and object.

Code explains better than i do, please see example.

Example

myComponent/redux.js:

import { createState } from 'redux-msg';

const NAME = 'myComponent';
const MODEL = {
  default: 'property',
  something: 'i am some default value'
};

export const state = createState(NAME)(MODEL);

create-store.js:

createStore from redux accepts second parameter - initial state. this is where createState may be used

import { createStore, combineReducers } from 'redux';
import myComponent from 'myComponent/redux';

const store = createStore(
  combineReducers({
    [myComponent.NAME]: myComponent.reducer
  }),
  {
    ...createMyComponentState({ something: 'i am NOT default haha!' })
  })

after this, store.getState() will return:

{
  'myComponent': {
    default: 'property'
    something: 'i am NOT default haha!'
  }
}