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Mobx-based store for async data fetching and state management. https://iunu.github.io/mobx-async-store/

Table of Contents


mobx-async-store was designed to consume JSON::API specification compliant REST APIs and provide a state management system for conveniently manipulating client-side data and keeping it in sync with the server-side.

The library uses mobx internally to provide reactivity and observability; i.e when you fetch data from the server or make changes to client-side records then the UI should update accordingly. This system has only be tested in combination with mobx-react, but should hypothetically work with libraries like mobx-vue or mobx-angular.

Development setup

Clone this repository and install its dependencies:

git clone git@github.com:iunu/mobx-async-store.git cd mobx-async-store yarn install


yarn test will run all tests.


Step 1 - Build the dist files

yarn build builds the library to dist, generating two files:

  • dist/mobx-async-store.cjs.js A CommonJS bundle, suitable for use in Node.js, that requires the external dependency. This corresponds to the "main" field in package.json
  • dist/mobx-async-store.esm.js an ES module bundle, suitable for use in other people's libraries and applications, that imports the external dependency. This corresponds to the "module" field in package.json

Step 2 - Update the documentation

yarn docs updates the documentation, located in docs.

Step 3 - Publish

npm login to authenticate yourself as someone authorized to publish this package npm publish (or npm publish =tag=develop for development releases)


yarn add mobx-async-store


mobx-async-store uses two main classes, Store and Model. Subclasses of Model are used to instantiate data objects, and Store provides an interface to add and manipulate those objects.


You can define models by extending them and adding your own property definitions. The static property type determines how the store and other objects will refer to the class (corresponds to type in a jsonapi document), and endpoint defines the path the model will use to the server. Definitions are stored in two hashes that are static properties on the model, attributeDefinitions and relationshipDefinitions. These definitions determine how data will be parsed and implemented as it is returned from the server.

import { Model } from 'mobx-async-store' class Todo extends Model { static type = 'todos' static endpoint = 'todos' static attributeDefinitions = { title: { transformer: stringType, validator: validatesString, defaultValue: 'NEW TODO' } } static relationshipDefinitions = { notes: { direction: 'toMany', validator: validatesArrayPresence, types: ['notes', 'awesome_notes'], inverse: { name: 'todo', direction: 'toOne' } } } }


The attributeDefinitions hash corresponds to the attributes hash of a jsonapi document. It is defined by keys representing the names of the properties, and objects with definitions of those properties.

  • transformer - a function used to coerce the value to a given type or format
  • validator - a function used to determine whether a key is allowed or not
  • defaultValue - the value that is used on a new instance if none is defined


The relationshipDefinitions hash corresponds to relationships in a jsonapi document. It is defined by keys representing the names of the relationships, and objects with defintions of those properties.

  • direction - can be toOne or toMany
  • validator - a function used for validating a relationship
  • types - an array of polymorphic model types that can be used for this relationship
  • inverse - the other direction of a relationship. Not required, but allows models to be related both directions without explicitly defining both directions
    • name - the name the relationship uses to refer to this model. This is automatically inferred if it matches the model type (usually for toMany relationships)
    • direction - the inverse direction, toOne or toMany

Model methods and properties

See jsdoc documentation


The store is used to collect, retrieve and refer to documents.

import AppStore from './AppStore' const store = new AppStore({ baseUrl: 'https//api.example.com', defaultFetchOptions: { headers: { 'Accepts': 'application/json', 'Content-Type': 'application/vnd.api+json', 'X-CSRF-Token': 'EXAMPLE-CSRF-TOKEN' } }, headersOfInterest: ['X-Iunu-Roots'], retryOptions: { attempts: 3, delay: 1000, }, errorMessages: { 400: 'Bad request.', 403: 'Forbidden', ... default: 'Something went wrong.', } })

Retrieving documents

The store uses variations of get, find and fetch to retrieve records from the store, with All, Many, and One determining how many records will be requested. An optional options hash provides further customization for requesting and caching.

  • get will only retrieve locally cached records, and will never request from the server
  • find will first look for records of a given type in the store, and then will go to the server
  • fetch will always request from the server
  • getAll, findAll, and fetchAll retrieve all records that match the optional options
    • store.getAll('todos', { queryParams: { recent: true } })
  • getOne, findOne, and fetchOne retrieves one record. Usually used with just one id but can also use the options hash.
    • store.getOne('todos', '1')
  • getMany, findMany, and fetchMany are like One but with an array of ids instead of a single id
queryParams options

mobx-async-store builds queries that are JSON::API compliant. Requests are cached from the previous call - including any queryParams given.

store.findAll('todos', { queryParams: filter: { title: 'Do taxes', filter: { overdue: true } } }) // The query is: '/example_api/todos?filter[title]=Do taxes&filter[overdue]=true' // This fetches from the server and stores the result of the query in the cache. store.findAll('todos', { queryParams: filter: { title: 'Do taxes', filter: { overdue: true } } }) // Returns result from the cache.


FactoryFarm to quickly build data models that can be used for testing. An instance of FactoryFarm has factories defined that can be used to build models at runtime.

Defining a factory You can define a factory for any model in shared-js/store. Then, objects can be built using the predefined factory, which describes attributes and relationships.

const factoryFarm = new FactoryFarm() factoryFarm.define('funZone', { type: 'zones', name: 'Fun Zone' })

const funZone = factoryFarm.build('funZone') funZone.name => 'Fun Zone'

Factories follow an inheritance tree which can be used to override some properties while keeping the other parent properties.

const factoryFarm = new FactoryFarm() factoryFarm.define('funZone', { type: 'zones', name: 'Fun Zone' }) factoryFarm.define('bigZone', { parent: 'funZone', seeding_unit_capacity: 1000 })

const funZone = factoryFarm.build('bigZone') funZone.name => 'Fun Zone' funZone.seeding_unit_capacity => 1000

FactoryFarm from utils/Testing comes pre-loaded with a number of factories. Most are singularized versions of the model name.

Factories and relationships Factories can be used to build relationships just as you would with mobx-async-store.

const factoryFarm = new FactoryFarm() const seeding_unit = factoryFarm.build('seeding_unit', { name: 'Seeding Unit 1') factoryFarm.define('bigZone', { parent: 'funZone', seeding_unit })

const funZone = factoryFarm.build('funZone') funZone.seeding_unit.name => 'Seeding Unit 1'

Dynamic factories Attributes and relationships can be defined as functions. The function will be executed at build. Passing a third parameter while building will return an array of objects.

const factoryFarm = new FactoryFarm() factoryFarm.define('dynamicZone', { parent: 'funZone', name: (index, properties) => Fun Zone ${properties.id}, seeding_unit: () => factoryFarm.build('seeding_unit'), })

const facility = factoryFarm.build('facility', { name: 'Jay St' })

const dynamicZones = factoryFarm.build('dynamicZone', { facility }, 2) const [zone1, zone2] = dynamicZones

zone1.name => 'Fun Zone 1' zone1.seeding_unit.name => 'Seeding Unit 1' zone1.facility.name => 'Jay St' zone2.name => 'Fun Zone 2' zone2.seeding_unit.name => 'Seeding Unit 2' zone2.facility.name => 'Jay St'

More on Server Calls MockServer uses an internal factory and store to simulate data to return during a fetch. For GET requests, it will first try to return a defined object from the store. If that misses, it will return an object from the default factory. PATCH requests return the properties that were sent, and POST requests return a new object with the properties that were sent with a new id. Special cases such as defining specific routes (eg for external apis), delayed responses (for race conditions), and error states are described below.

Example with a component

// Component @inject('dataStore') class Button extends Component { @observable zone changeZoneName = (name) => { const { zone } = this zone.name = name zone.save() } componentDidMount() { this.loadData() }

loadData = async () { const { dataStore, zoneId } = this.props this.zone = await dataStore.fetchOne('zones', zoneId) } render () { const { name } = this.zone?.name const { changeZoneName } = this return <button onClick={() => changeZoneName('Zone 2')}>{name} } }

// Test describe('it changes the zone name', () => { let wrapper

beforeEach(() => { mockServer.start()

wrapper = mount( <TestContextWrapper> <Button zoneId='1' /> </TestContextWrapper> ) setImmediate((done) => { wrapper.update() done() })


it('changes zone name when clicked', () => { expect(wrapper.text()).toMatch('Zone 1') wrapper.find('button').simulate('click') expect(wrapper.text()).toMatch('Zone 2') expect(fetch.mock.calls).toHaveLength(2) const [fetchZone, patchZone] = fetch.mock.calls expect(fetchZone[0].method).toEqual('GET') expect(fetchZone[0].body).toMatch('Zone 1') expect(fetchZone[0].method).toEqual('PATCH') expect(fetchZone[0].body).toMatch('Zone 2') }) })

Example with a helper

export const fetchZone = (zoneId) { return dataStore.fetchOne('zones', zoneId) }

// Test describe('fetchZone', () => { let factoryFarm let wrapper

beforeEach(() => { const mockServer = new MockServer() mockServer.start() })

it('loads the zone', async (done) => { const zone = await fetchZone('1') expect(zone.name).toMatch('Zone 1') expect(fetch.mock.calls).toHaveLength(1) expect(fetch.mock.calls[0].method).toEqual('GET') }) })

Example - failure on specific call

// Testing a catch alerts with errors it('returns errors if saving fails', async (done) => { expect.assertions(3) // Include non 200 status in response override (default is 200) const responseOverrides = [ { path: '/new/completions', method: 'POST', status: 500, response: () => { return { errors: [{ title: 'Invalid options', detail: 'There is an error!', meta: { server: true } }], } }, }, ]

// Pass in response overrides when starting the server const mockServer = new MockServer() mockServer.start({ responseOverrides }) window.alert = jest.fn() expect(fetch.mock.calls).toHaveLength(1) const submitBtn = wrapper.find('button[data-testid="manual-task-submit-button"]') await submitBtn.simulate('click') expect(fetch.mock.calls).toHaveLength(2) setImmediate(() => { expect(window.alert).toHaveBeenCalledWith('There is an error!') done() })


Example - failure on all calls

// Testing a catch alerts with errors it('returns errors if saving fails', async (done) => { expect.assertions(2)

// Pass in non-200 status when starting the server (this will fail all responses) const mockServer = new MockServer() mockServer.start({ status: 500 }) expect(fetch.mock.calls).toHaveLength(1) const submitBtn = wrapper.find('button[data-testid="manual-task-submit-button"]') try { await submitBtn.simulate('click') } catch (error) { expect(fetch.mock.calls).toHaveLength(2) }


Customizing Data You can pass in a factory or store to define data that will be returned by the server, using the factoryFarm and store in the constructor options. Passing factoriesForType will allow you to use a defined factory for mocking data instead of the default factory.

// Component @inject('dataStore') class Button extends Component { @observable zone

componentDidMount() { this.loadData() }

loadData = async () { const { dataStore, zoneId } = this.props this.zone = await dataStore.fetchOne('zones', zoneId) }

render () { const { name } = this.zone?.name const { changeZoneName } = this return <button onClick={() => changeZoneName('Zone 2')}>{name} } }

// Test describe('it displays the zone name', () => { let factoryFarm let wrapper

beforeEach(() => { const mockServer = new MockServer() mockServer.define('funZone', { name: (index) => Fun Zone ${index} })

mockServer.start({ factoriesForType: { zones: 'funZone' }, }) wrapper = mount( <TestContextWrapper> <Button zoneId='1'/> </TestContextWrapper> ) setImmediate((done) => { wrapper.update() done() })


it('displays the zone name', () => { expect(wrapper.text()).toMatch('Fun Zone 1') expect(fetch.mock.calls).toHaveLength(1) expect(fetch.mock.calls[0].method).toEqual('GET') }) })

Complex Setup responseOverrides will take a hash of responses and use those to match fetch calls, overriding the server’s calls to the store. delayedResponse, in conjunction with serverResponse, adds a timeout to the promise to simulate a delay in returning from the server.


errorMessages: These are optional error messages that can be configured to provide additional details when returning errors for various requests. Each property corresponds to an HTTP status code which can be customized, and any errors returned from the server that have a status matching this code will have their detail property overriden by this value. A default can also be set as a fallback.

Persisting records with Model#save

Records created on client side can be persisted via an AJAX request by calling the save method on the record.

const todo = store.add('todos', { title: 'Buy Milk', category: 'chores' }) // POST /todos await todo.save()

If the server responds to a save with a status code that is not 200 or 201, then the Model#errors object will populated by matching source pointers from the response to the attributes on the model.

Handling errors

If any fetch, save, or destroy fails, the query will return a rejected promise with an error containing any JSONAPI errors returned with the response. If no errors are present, then the response status will be converted to an error and returned with the corresponding configured error message.

For example, if the server returns a 500 response with no body for a fetchOne, then the error returned will be

[ { detail: "Something went wrong.", status: 500 } ]

This value will always be a stringified JSON array, so you can handle errors as such:

try { await store.fetchMany('todos', ids); } catch (error) { const errors = JSON.parse(error.message); console.log(errors[0].detail); // "Something went wrong." console.log(errors[0].status); // 500 }


Last updated on 21 Feb 2023

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