exampleSelector.js

import { createSelector } from 'reselect';
import _ from 'lodash';

const contractDataSelector      = state => state.contracts.data;
const currentContractIdSelector = state => state.contracts.currentId;

const contractSelectors = {

  contracts() {
    createSelector([contractDataSelector],
      (data) => data)
  },

  contractsGroupedByCommodity() {
    createSelector([this.contracts],
      (items) => _.groupBy(items, item => item.commodity.id)
  )},

  purchaseContractsGroupedByCommodity() {
    createSelector([contractDataSelector],
      (items) => {
        debugger
        let results = _.chain(items)
                // .filter(contract => contract.kind === 'Purchase')
                .groupBy(contract => contract.commodity.id)
        console.debug(' selector results :', results );
        return results;
      }
  )},

  currentContract() {
    createSelector([currentContractIdSelector, this.contracts],
      (items, id) => {
        if (items && id) {
          return items[id]
        }
     })
  },

}

export default contractSelectors;