mergeChildReducers(parentResult, action, childMap)

NOTE: mergeChildReducers is deprecated as of version 6.0.0. It will be removed in 7.0.0. combineReducers and reduceReducers should cover the cases where mergeChildReducers is needed. If you need to use it temporarily without a console warning, use DEPRECATED_mergeChildReducers(parentResult, action, childMap). This will also be removed in 7.0.0 though.

mergeChildReducers is a more generalized version of combineReducers that allows you to nest reducers underneath a common parent that has functionality of its own (rather than restricting the parent to simply passing actions to its children like combineReducers does)

  • parentResult: Object | loop(Object, Cmd) – The result from the parent reducer before any child results have been applied.

  • action: Action – a redux action

  • childMap: Object<string, ReducerFunction> – a plain object map of keys to nested reducers, similar to the map in combineReducers. However, a key can be given a value of null to have it removed from the state.


import {getModel, isLoop, mergeChildReducers} from 'redux-loop';
import pageReducerMap from './page-reducers';

// a simple reducer that keeps track of your current location and nests the correct
//child reducer for that location at

const initialState = {
   location: 'index'
   //data will be filled in with the result of the child reducer

function parentReducer(state = initialState, action){
  if(action.type !== 'LOCATION_CHANGE')
     return state;

  return {...state, location: action.newLocation};

export default function reducer(state, action){
  const parentResult = parentReducer(state, action);

  let location;
    location = getModel(parentResult).location;
    location = parentResult.location;

  const childMap = {data: pageReducerMap[location]};

  return mergeChildReducers(parentResult, action, childMap);

Passing extra params

If you pass extra parameters to mergeChildReducers, they will be passed through to each nested reducer.

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