rereduce - Reducer library for Redux

jopen 8年前

Rereduce

Simple reducer library for Redux. It's like Reselect but for reducers.

Reducers can depend on each others.

It permits to replace the imperative waitFor of original Flux implementation by a purely functional approach.

/!\ Work in progress: Current implementation does not play well (yet) with server-side rendering or time-travel.

API

createReducer( [reducerDependencies], reducerFunction)

[reducerDependencies] is an optional object that looks like {key1: reducer1, key2: reducer2}

If dependencies are provided, reducerFunction will be called with a 3rd argument with the state of the dependency reducers.

Note that the API is a first draft and may change in the future. Don't hesitate to discuss what the API should look like here: https://github.com/slorber/rereduce/issues/1

Simple example

import {  createReducer  } from 'rereduce'    // Create a simple reducer without dependencies  const firstReducer =  createReducer(function(state = 0, action) {    switch (action.type) {      case 'increment': return state + 1      case 'decrement': return state - 1      default: return state    }  })    // Create another reducer that depends on first reducer  const secondReducer = createReducer({ firstReducer }, // declare dependency to firstReducer    function(state = 0,action,{firstReducer}) {      return firstReducer + 1    }  )    // Everytime secondReducer is called, firstReducer will also be called  // firstReducer is memoized so it is not inefficient to call it multiple times

How it works

What it does in reality:

  • It memoizes reducers so that they can be reused efficiently
  • It permits to create reducers depending on other reducers

The core logic is simple, it's just 10 lines of code :) the rest is FP utility code. 

export function createReducer() {    const { reducerDependencies,reducer,reducerMemoizer } = parseArgs(arguments)      // This variable tracks the state of the reducer dependencies    // These states are all initialized to undefined    let reducerStates = mapValues(reducerDependencies,() => undefined)      const liftedReducer = function(state, action) {      // Compute reducer dependency states      reducerStates = mapValues(reducerStates,(state,key) => {        return reducerDependencies[key](state,action)      })      // Call reducer function provided by user and injects reducer dependency states      return reducer(state,action,reducerStates)    }    // Memoize the reducer so that it can be used efficiently as a dependency to other reducers    return reducerMemoizer(liftedReducer)  }

Unit test

import {  createReducer  } from 'rereduce'    const a =  createReducer((state = 0, action) => {    switch (action.type) {      case 'increment': return state + 1      case 'decrement': return state - 1      default: return state    }  })    const b =  createReducer((state = 5, action) => {    switch (action.type) {      case 'increment': return state + 10      case 'decrement': return state - 10      default: return state    }  })    const c = createReducer({ a,b }, (state = 0,action,{ a,b }) => {    const sum = a + b    return state + sum  })    const d = createReducer({ c }, (state = 0,action,{ c }) => {    return c + 1  })    const counters = combineReducers({ a, b , c, d })    let state    state = counters(state, { type: 'init' })  assert.equal(state.a, 0)  assert.equal(state.b, 5)  assert.equal(state.c, 5)  assert.equal(state.d, 6)    state = counters(state, { type: 'increment' })  assert.equal(state.a, 1)  assert.equal(state.b, 15)  assert.equal(state.c, 21)  assert.equal(state.d, 22)

项目地址： https://github.com/slorber/rereduce