Code Reading - Shared React Form Library

Published Thursday, January 12, 2017

Notes from code reading on Flatiron School eng team’s shared React from library by Seiji Naganuma.


React is not an opionated library

  • too many options for building forms
  • we ended up with a bunch of different implementations / approaches

Forms are omnipresent in our app

  • lots of repeated code
  • need to DRY this up


  • Build out library to manage form state + validation + submission
  • Build reusable form component specific to our domain


  • Reviewed all our current approaches
  • Melded into single, shareable component

Shared Component Library

Can be used for controlled + uncontrolled inputs

  • examples at /admin/react/forms
  • documentation on ironboard wiki

Robust test coverage

Default styles can be overridden

Acts as building block / starting point for new form

  • won’t just magically build your entire form for you
  • use lego blocks to build lego set

Alt Form: existing library, but outdated and not super functional, so Seiji rebuilt one specific to our app

Uses Curring pattern

  • Referred to in React community as “high order component”

3 Objects:

  1. Form Object
  2. Form Component
  3. Form Connector
Form Object      Form Component
     \                 /
      \               /
        Form Connector
        React Form


Goal: build form with first name, last name submittable inputs

Walkthrough (propriety code omitted)

  1. Create FormComponent
    • updates UI on state changes
    • holds Input and Button components
  2. Build FormObject
    • stores field configuration
    • underlying implementation: AltStore
    • dispatch actions through Alt dispatcher
    • uses global Alt instance to dispatch events, so will need to namespace events
    • object that’ll have field names (keys)
    • values are the validation functions
    • to declare something invalid, throw an Error
  3. Import FormConnector
    • connector syncs FormObject and FormComponent states
    • render ConnectedForm into DOM
    • connector gives us lotsa good props to use
    • passes FormObject into FormComponent, returns React component w/ everything needed to render
  4. Import individual input components from shared react components (ex. TextFieldInput, etc)
    • Use REST spread syntax to pass fields into props:
// generic example
var props = {
  a: 'hello',
  b: 'world'
var {a,} = props

// input component example
const {fields} = this.props

  labelText='Cool label'
  1. Question: how to validate server-side?
    • might need more configuration, but FormObject does handle onFormSubmitFailure
  2. Sending data to server
    • configure onSubmit function on FormObject
    • takes in current form state
    • that function makes a POST request to whatever endpoint


Bit of a learning curve, but should help standardize our forms.

Handles decision making for you

Abstracts out state management

Goal: open source this project

  • good resource for Alt users
  • nothing else out there as good as ReactForms