Formik Effect

Declarative Formik component for side-effects. Use with caution. Please. I. beg. you.

yarn add @onaio/formik-effect --save

Note: this has peer dependencies of react, and formik.

The Problem

Formik is an uncontrolled component. However, there are times when you want to trigger a side effect based on a state change. By design, Formik does not expose a prop for you to do this because I'm terrified as to how it would be abused--it encourages people to attempt to "sync" Formik's state in elsewhere (cough like in a Redux store cough cough). Anyways, please don't do that. You never ever ever ever want to store the same state in 2 places in a React application because it is almost impossible to keep them in sync unless you are a goddamn jedi. You may think it's working, and high five a teammate, but you are a just a lifecycle method away from lots and lots of pain and I can guarantee you are not considering all the edge cases. Sooooo....

SAY IT WITH ME:

"I WILL NOT USE THIS TO STORE FORMIK STATE ELSEWHERE IN MY APP."

"I WILL NOT USE THIS TO STORE FORMIK STATE ELSEWHERE IN MY APP."

"I WILL NOT USE THIS TO STORE FORMIK STATE ELSEWHERE IN MY APP."

Basic Usage

Import the component and put it inside any Formik form. It renders null! Pass it an onChange() function and it will be called whenever your Formik form's state updates.

import React from 'react';
import { Formik, Field, Form } from 'formik';
import { FormikEffect } from '@onaio/formik-effect';

export const SignupForm = () => (
  <div>
    <h1>My Cool Form with a SideEffect</h1>
    {/* tslint:disable jsx-no-lambda */}
    {/* tslint:disable no-console */}
    <Formik
      onSubmit={values => console.log(values)}
      initialValues={{ firstName: '', lastName: '', email: '' }}
    >
      {() => (
        <Form translate="yes">
          <FormikEffect onChange={(currentFormikState, nextFormikState) => {
               // do whatevs
               // FYI if you alter state it will cause another render
            }};
          <Field id="firstName" name="firstName" placeholder="First Name" />
          <Field id="lastName" name="lastName" placeholder="Last Name" />
          <Field name="email" type="email" placeholder="Email Address" />
          <button type="submit">Submit</button>
        </Form>
      )}
    </Formik>
    {/* tslint:enable jsx-no-lambda */}
    {/* tslint:enable no-console */}
  </div>

API

Only one!

onChange: (currentState: FormikState, nextState: FormikState) => void

Put your side effect here.

FormikState includes:

• values
• errors
• touched
• isSubmitting

Inspiration

This package was inspired by, and builds heavily on, the original formik-effect package written by Jared Palmer.