updating a collection

replaceItem.js

import { always, map, propEq, when } from 'ramda'

let replaceItem = (item, list) =>
  map(when( propEq('id', item.id) , always(item)), list)

export default replaceItem

replaceItem.test.js

import replaceItem from './replaceItem'

describe('replaceItem', function() {
  test('replaces an item in a collection in place by id', function() {
    let state = [
      {id: 1, name: 'one'}, 
      {id: 2, name: 'two'},
      {id: 3, name: 'three'}
    ]

    let update = {id: 2, color: 'green' }

    let expected = [
      {id: 1, name: 'one'}, 
      {id: 2, color: 'green'}, 
      {id: 3, name: 'three'}
    ]

    expect(replaceItem(update, state)).toMatchObject(expected)
  })
})

updateItem.js

import { eqProps, ifElse, map, mergeDeepLeft } from 'ramda'

let idsEq = eqProps('id')
let identity = x => x

let updateItem = update =>
  map(ifElse(
    idsEq(update),
    mergeDeepLeft(update),
    identity)
  )

export default updateItem

updateItem.test.js

import updateItem from './updateItem'

describe('updateItem', function() {
  test('finds an item in a collection by id and updates relevant properties', function() {
    let state = [
      { id: 1, name: 'one', items: []},
      { id: 2, name: 'two',items: []},
      { id: 3, name: 'three', items: []}
    ] 

    let updatedItem = {id: 2, name: 'new name', items: [{one: 1}]}

    let expected = [
      { id: 1, name: 'one', items: []},
      { id: 2, name: 'two', name: 'new name', items: [{one: 1}]},
      { id: 3, name: 'three', items: []}
    ] 

    let update = updateItem(updatedItem)
    let updatedCollection = update(state)

    expect(updatedCollection).toMatchObject(expected)
  })
  test('adds a property to a collection item', function() {
    let state = [
      { id: 1, items: []},
      { id: 2, items: []},
      { id: 3, items: []}
    ] 

    let updatedItem = {id: 2, newProp: 42}

    let expected = [
      { id: 1, items: []},
      { id: 2, items: [], newProp: 42},
      { id: 3, items: []}
    ] 

    let update = updateItem(updatedItem)
    let updatedCollection = update(state)

    expect(updatedCollection).toMatchObject(expected)
  })
})

updateItem2.js

import { curry, eqProps, map} from 'ramda'

let idsEq = eqProps('id')

export let updateItem2 = curry((updated, collection) =>
  map(item => idsEq(item, updated) ? updated : item, collection)
)

i want to just update a collection by declaring the update and the collection. the above utils allow you to throw an object at a collection and either replace it or update its props by matching the id of the update with an id in a collection item.

// ensure the update has an id prop
let update = updateItem({id: 42, updatedProp: 43})
let collection = update(this.state.collection)
this.setState({ collection })