Redux Consumer Toolkit

This library implements several functions that are useful for combining, composing, and altering reducers and selectors (consumers). Each of this functions returns a memoized consumer, similar to reselect, so data isn't re-computed unnecessarily. The inspiration for this library was fantasyland-redux, only instead of basing it off of the fantasyland specification it is based off of the static-land specification. This made it simple to build this as a library instead of pinning it to a specific redux version.

See the Github Pages site for usage examples and documentation on the library. It is a literate program from which is constructed this library's source code.

API

The library is organized internally into modules corresponding to the structures defined by the static-land spec. However it exposes a more idiomatic Javascript API than what is specified in static-land. This overview will go over the idiomatic API.

The library assumes a traditional reducer signature of:

// Flow type
type Reducer<action, input, output> = (input, action) => output;

// Traditional signature
function reducer(state, action) {
  return state;
}

and a traditional selector signature of:

// Flow type
type Selector<props, input, output> = (input, props) => output;

// Traditional signature
function selector(state, props) {
  return state;
}

It unifies them into a single type called a consumer:

// Flow type
type Consumer<Static, Input Output> = (input, static) => output;

// Traditional signature
function consumer(input, static) {
  const output = input;
  return output;
}

Flow types are exported.

Both memoized and non-memoized versions of these modules are exported. Memoized versions can be accessed by importing from 'redux-consumer-toolkit/memoized' instead of 'redux-consumer-toolkit'.

Map

Use case

Modifying the returned state from a consumer.

• Pull only the properties that a specific component requires
• Derive computed properties from a reducer's state object

import { map } from 'redux-consumer-toolkit';

function grandTotal(receipt) {
  return receipt.shipping + receipt.tax + receipt.subtotal;
}

map(grandTotal, receiptReducer);

API

map : ((OutA => OutB), Consumer<Static, In, OutA>) => Consumer<Static, In, OutB>)

MapInOut

Use case

Modifying both the input state and the output state of a consumer.

• Glue consumers lower in the hierarchy to reducers higher in the hierarchy
• Embed consumers in a context like an object key or reversible transformation

import { mapInOut } from 'redux-consumer-toolkit';
import Ramda from 'ramda';

function grandTotal(receipt) {
  return receipt.shipping + receipt.tax + receipt.subtotal;
}

// Returns { lineItems, receipt }
const orderReducer;

// Ramda.prop gets the named property off an object
mapInOut(Ramda.prop('receipt'), grandTotal, orderReducer);

API

mapInOut : ((InA => InB), (OutA => OutB), Consumer<Static, InB, OutA>) => Consumer<Static, InA, OutB>

Objectify

Use case

Embed a consumer in an object.

objectify takes a key and a consumer and generates a consumer which can take an object with that key and return an object with that key. You can reimplement combineReducers this way.

import { objectify, identity, expandAll } from 'redux-consumer-toolkit';

const combineReducers = (reducerSpec) => (
  reducerSpec.map((r, k) => objectify(k, r))
    .reduce(expandAll, identity)
)

API

objectify : (string, Consumer<Static, In, Out>) => Consumer<Static, { string: In }, { string: Out }>

MapIn

Use case

Like mapInOut, but only change the input of a consumer.

API

mapIn : ((InA => InB), Consumer<Static, InB, Out>) => Consume<Static, InA, Out>

ApAll

Use case

Take transformation functions you would use with map, but have multiple arguments, and apply them to multiple consumer. Each consumer gets the same action/props and input state.

import { apAll } from 'redux-consumer-toolkit';

const grandTotal = (shipping, tax, subtotal) => {
  return shipping + tax + subtotal;
};

apAll(of(grandTotal), shippingReducer, taxReducer, subtotalReducer);

API

apAll : (Consumer<Static, In, (mixed  => Out)>, ...Array<Consumer<Static, In, mixed>>) => Consumer<Static, In, Out>

Constant

Use case

Provides a way to take non-consumer things like functions and values and use them with apAll. It essentially creates a consumer that always returns the same value. See the use case for apAll for an example.

API

constant: (Out) => Consumer<Static, In, Out>

ConcatAll

Use case

Provides a way to take two (or more) consumers and run them with the same action/props, one after the other. The output of the first consumer is used as input to the second consumer.

import { concatAll } from 'redux-consumer-toolkit';

// Returns line items state
const lineItemsReducer;
// Takes line items and returns a total
const subtotalReducer;

concatAll(lineItemsReducer, subtotalReducer);

API

concatAll : (Consumer<Static, In, OutA>, Consumer<Static, OutA, OutB>) => Consumer<Static, In, OutB>

Identity

Use case

Provides a special consumer that can be used as an identity when combining reducers using concat. This is handy if you have a list of reducers you want to reduce over and need an initial value.

API

identity : Consumer<Static, In, In>

Chain

Use case

Provides a way to combine consumers in such a way that the second consumer's behavior can depend on the output of the first. Both consumers receive the same input and static values. This is useful for consumers that depend on the values of other consumers in addition to their own internal state. This is a powerful but fairly low-level ability. Therefore some convenience functions are specified here as well for common combinations.

import { chain, mapIn } from 'redux-consumer-toolkit';
import Ramda from 'ramda';

// This consumer depends on the router state to know when to load more products
const productListReducer = (router) => (state, action) => { ... };

chain((routerState) => (
  mapIn(Ramda.prop('productList'), productListReducer(router))
), mapIn(Ramda.prop('router'), routerReducer));

API

chain : (Consumer<Static, In, OutA>, OutA => Consumer<Static, In, OutB>) => Consumer<Static, In, OutB>

ExpandAll

Use case

expandAll handles the use case where you might want consumers operating on the same state to each return separate keys of a resulting object.

import { expandAll } from 'redux-consumer-toolkit';

// Manages user account information
const userReducer;
// Manages cart information, the cart may be anonymous or registered to a user.
const cartReducer;

// We might want to have all the cart and user information available in the same
// object
expandAll(userReducer, cartReducer);

API

expandAll : (...Consumer<Static, In, *>) => Consumer<Static, In, Out>

Combine

Use case

combine works just like the traditional combineReducers function, but it can also operate on selectors. It also lacks the beginner-friendly runtime checks that combineReducers provides. It accepts an object whose values are consumers, and returns a consumer that will generate an object with the same keys whose values are the state returned from the individual consumers.

API

combine : (Object<string, Consumer<Static, In, *>>) => Consumer<Static, In, Out>

Utilities

There are some utility functions to help debug consumers.

LogConsumer

Log the output of the consumer before returning it.

logConsumer('message', consumer)

DebugConsumer

Enters a breakpoint before returning the output of the consumer for easy examination.

debugConsumer(consumer)

Contributing

Requires webpack, babel, and eslint to build. You can use a Nix shell to enter a development environment with those tools already in it or just use your own.