formik-old

Overview

Let's face it, forms are really verbose in React. To make matters worse, most form helpers do wayyyy too much magic and often have a significant performance cost associated with them. Formik is a small library that helps you with the 3 most annoying parts:

1. Getting values in and out of form state
2. Validation and error messages
3. Handling form submission

By colocating all of the above in one place, Formik will keep things organized--making testing, refactoring, and reasoning about your forms a breeze.

Developer Experience

I wrote Formik while building a large internal administrative dashboard with Ian White. With around ~30 unique forms, it quickly became obvious that we could benefit by standardizing not just our input components but also the way in which data flowed through our forms.

Why not Redux-Form?

By now, you might be thinking, "Why didn't you just use Redux-Form?" Good question.

1. According to our prophet Dan Abramov, form state is inherently emphemeral and local, so tracking it in Redux (or any kind of Flux library) is unnecessary
2. Redux-Form calls your entire top-level Redux reducer multiple times ON EVERY SINGLE KEYSTROKE. This is fine for small apps, but as your Redux app grows, input latency will continue increase if you use Redux-Form.
3. Redux-Form is 22.5 kB minified gzipped (Formik is 9.2 kB)

My goal with Formik was to create a scalable, performant, form helper with a minimal API that does the really really annoying stuff, and leaves the rest up to you.

Influences

Formik started by expanding on this little higher order component by Brent Jackson, some naming conventions from Redux-Form, and (most recently) the render props approach popularized by React-Motion and React-Router 4. Whether you have used any of the above or not, Formik only takes a few minutes to get started with.

Installation

Add Formik to your project.

npm i formik --save

You can also try before you buy with this demo of Formik on CodeSandbox.io

Demos

• Basics
• Sync Validation
• Building your own input primitives
• Working with 3rd-party inputs #1: react-select
• Working with 3rd-party inputs #2: Draft.js
• Accessing React lifecycle functions

Talks

• An Introduction to Formik by Jared Palmer @ Spotify NYC. August 15th, 2017.

Community Articles / Tutorials

• The Joy of Forms with React and Formik
• Painless React Forms with Formik

The gist

Formik keeps track of your form's state and then exposes it plus a few reusable methods and event handlers (handleChange, handleBlur, and handleSubmit) to your form via props. handleChange and handleBlur work exactly as expected--they use a name or id attribute to figure out which field to update.

There are two ways to use Formik:

• withFormik(): A Higher-order Component (HoC) that accepts a configuration object
• ``: A React component with a render prop

Both do exactly the same thing and share the same internal implementation. They just differ in their respective style....

// Higher Order Component
import React from 'react';
import { withFormik } from 'formik';

// Our inner form component which receives our form's state and updater methods as props
const InnerForm = ({
  values,
  errors,
  touched,
  handleChange,
  handleBlur,
  handleSubmit,
  isSubmitting,
}) => (
  <form>
    <input value="{values.email}" name="email" type="email">
    {touched.email &amp;&amp; errors.email &amp;&amp; <div>{errors.email}</div>}
    <input value="{values.password}" name="password" type="password">
    {touched.password &amp;&amp; errors.password &amp;&amp; <div>{errors.password}</div>}
    <button disabled="{isSubmitting}" type="submit">
      Submit
    </button>
  </form>
);

// Wrap our form with the using withFormik HoC
const MyForm = withFormik({
  // Transform outer props into form values
  mapPropsToValues: props =&gt; ({ email: '', password: '' }),
  // Add a custom validation function (this can be async too!)
  validate: (values, props) =&gt; {
    let errors = {};
    if (!values.email) {
      errors.email = 'Required';
    } else if (
      !/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i.test(values.email)
    ) {
      errors.email = 'Invalid email address';
    }
    return errors;
  },
  // Submission handler
  handleSubmit: (
    values,
    {
      props,
      setSubmitting,
      setErrors /* setValues, setStatus, and other goodies */,
    }
  ) =&gt; {
    LoginToMyApp(values).then(
      user =&gt; {
        setSubmitting(false);
        // do whatevs...
        // props.updateUser(user)
      },
      errors =&gt; {
        setSubmitting(false);
        // Maybe even transform your API's errors into the same shape as Formik's!
        setErrors(transformMyApiErrors(errors));
      }
    );
  },
})(InnerForm);

// Use  anywhere
const Basic = () =&gt; (
  <div>
    <h1>My Form</h1>
    <p>This can be anywhere in your application</p>
    
  </div>
);

export default Basic;

// Render Prop
import React from 'react';
import { Formik } from 'formik';

const Basic = () => (
  <div>
    <h1>My Form</h1>
    <p>This can be anywhere in your application</p>
    {/*
      The benefit of the render prop approach is that you have full access to React's
      state, props, and composition model. Thus there is no need to map outer props
      to values...you can just set the initial values, and if they depend on props / state
      then--boom--you can directly access to props / state.

      The render prop accepts your inner form component, which you can define separately or inline
      totally up to you:
      - ` <form>...</form>}&gt;`
      - ``
      - `{props =&gt; <form>...</form>}` (identical to as render, just written differently)
    */}
     {
        // same as above, but feel free to move this into a class method now.
        let errors = {};
        if (!values.email) {
          errors.email = 'Required';
        } else if (
          !/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i.test(values.email)
        ) {
          errors.email = 'Invalid email address';
        }
        return errors;
      }}
      onSubmit={(
        values,
        { setSubmitting, setErrors /* setValues and other goodies */ }
      ) =&gt; {
        LoginToMyApp(values).then(
          user =&gt; {
            setSubmitting(false);
            // do whatevs...
            // props.updateUser(user)
          },
          errors =&gt; {
            setSubmitting(false);
            // Maybe transform your API's errors into the same shape as Formik's
            setErrors(transformMyApiErrors(errors));
          }
        );
      }}
      render={({
        values,
        errors,
        touched,
        handleChange,
        handleBlur,
        handleSubmit,
        isSubmitting,
      }) =&gt; (
        <form>
          <input value="{values.email}" name="email" type="email">
          {touched.email &amp;&amp; errors.email &amp;&amp; <div>{errors.email}</div>}
          <input value="{values.password}" name="password" type="password">
          {touched.password &amp;&amp; errors.password &amp;&amp; <div>{errors.password}</div>}
          <button disabled="{isSubmitting}" type="submit">
            Submit
          </button>
        </form>
      )}
    /&gt;
  </div>
);

export default Basic;

Complementary Packages

As you can see above, validation is left up to you. Feel free to write your own validators or use a 3rd party library. Personally, I use Yup for object schema validation. It has an API that's pretty similar Joi / React PropTypes but is small enough for the browser and fast enough for runtime usage. Because I ❤️ Yup sooo much, Formik has a special config option / prop for Yup called [validationSchema] which will automatically transform Yup's validation errors into a pretty object whose keys match [values] and [touched]. Anyways, you can install Yup from npm...

npm install yup --save

Table of Contents

• Usage
  • Simple Example
• API
  • ``
    • Formik render methods
    • Formik props
      • dirty: boolean
      • errors: { [field: string]: string }
      • handleBlur: (e: any) => void
      • handleChange: (e: React.ChangeEvent) => void
      • handleReset: () => void
      • handleSubmit: (e: React.FormEvent) => void
      • isSubmitting: boolean
      • isValid: boolean
      • resetForm: (nextValues?: Values) => void
      • setErrors: (fields: { [field: string]: string }) => void
      • setFieldError: (field: string, errorMsg: string) => void
      • setFieldTouched: (field: string, isTouched: boolean) => void
      • setFieldValue: (field: string, value: any) => void
      • setStatus: (status?: any) => void
      • setSubmitting: (boolean) => void
      • setTouched: (fields: { [field: string]: boolean }) => void
      • setValues: (fields: { [field: string]: any }) => void
      • status?: any
      • touched: { [field: string]: boolean }
      • values: { [field: string]: any }
    • component
    • render: (props: FormikProps) => ReactNode
    • children: func
    • enableReinitialize?: boolean
    • isInitialValid?: boolean
    • initialValues?: Values
    • onSubmit: (values: Values, formikBag: FormikBag) => void
    • validate?: (values: Values) => FormikError | Promise
    • validateOnBlur?: boolean
    • validateOnChange?: boolean
    • validationSchema?: Schema | (() => Schema)
  • ``
  • <form>
  • withFormik(options)
    • options
      • displayName?: string
      • enableReinitialize?: boolean
      • handleSubmit: (values: Values, formikBag: FormikBag) => void
        • The "FormikBag":
      • isInitialValid?: boolean | (props: Props) => boolean
      • mapPropsToValues?: (props: Props) => Values
      • validate?: (values: Values, props: Props) => FormikError | Promise
      • validateOnBlur?: boolean
      • validateOnChange?: boolean
      • validationSchema?: Schema | ((props: Props) => Schema)
    • Injected props and methods
• Guides
  • React Native
    • Why use setFieldValue instead of handleChange?
    • Avoiding new functions in render
• Organizations and projects using Formik
• Authors
• Contributors

Usage

Simple Example

Imagine you want to build a form that lets you edit user data. However, your user API has nested objects like so.

{
   id: string,
   email: string,
   social: {
     facebook: string,
     twitter: string,
     // ...
   }
}

When we are done we want our dialog to accept just a user, updateUser, and onClose props.

// User.js
import React from 'react';
import Dialog from 'MySuperDialog';
import EditUserForm from './EditUserForm';
import { Formik } from 'formik';

const EditUserDialog = ({ user, updateUser, onClose }) => {
  const { email, social } = user;
  return (
    <dialog>
      <h1>Edit User</h1>
       {
          CallMyApi(user.id, values).then(
            updatedUser =&gt; {
              actions.setSubmitting(false);
              updateUser(updatedUser), onClose();
            },
            error =&gt; {
              actions.setSubmitting(false);
              actions.setErrors(transformMyAPIErrorToAnObject(error));
            }
          );
        }}
        render={({
          values,
          errors,
          touched,
          handleBlur,
          handleChange,
          handleSubmit,
          isSubmitting,
        }) =&gt; (
          
            <input value="{values.email}" name="email" type="email">
            {errors.email &amp;&amp; touched.email &amp;&amp; <div>{errors.email}</div>}
            <input value="{values.facebook}" name="facebook" type="text">
            {errors.facebook &amp;&amp;
              touched.facebook &amp;&amp; <div>{errors.facebook}</div>}
            <input value="{values.twitter}" name="twitter" type="text">
            {errors.twitter &amp;&amp; touched.twitter &amp;&amp; <div>{errors.twitter}</div>}
            <button disabled="{isSubmitting}" type="submit">
              Submit
            </button>
          
        )}
      /&gt;
    </dialog>
  );
};

To make writing forms less verbose. Formik comes with a few helpers to save you key strokes.

• ``
• <form>

This is the exact same form as before, but written with and:

// EditUserDialog.js
import React from 'react';
import Dialog from 'MySuperDialog';
import EditUserForm from './EditUserForm';
import { Formik, Field, Form } from 'formik';

const EditUserDialog = ({ user, updateUser, onClose }) => {
  const { email, social } = user;
  return (
    <dialog>
      <h1>Edit User</h1>
       {
          CallMyApi(user.id, values).then(
            updatedUser =&gt; {
              actions.setSubmitting(false);
              updateUser(updatedUser), onClose();
            },
            error =&gt; {
              actions.setSubmitting(false);
              actions.setErrors(transformMyAPIErrorToAnObject(error));
            }
          );
        }}
        render={({ errors, touched, isSubmitting }) =&gt; (
          
            
            {errors.email &amp;&amp; touched.email &amp;&amp; <div>{errors.email}</div>}
            
            {errors.facebook &amp;&amp;
              touched.facebook &amp;&amp; <div>{errors.facebook}</div>}
            
            {errors.twitter &amp;&amp; touched.twitter &amp;&amp; <div>{errors.twitter}</div>}
            <button disabled="{isSubmitting}" type="submit">
              Submit
            </button>
          
        )}
      /&gt;
    </dialog>
  );
};

API

``

`` is a component that helps you with building forms. In uses a render props pattern made popular by libraries like React Motion and React Router.

import React from 'react';
import { Formik } from 'formik';

const BasicExample = () => (
  <div>
    <h1>My Form</h1>
     {
        setTimeout(() =&gt; {
          alert(JSON.stringify(values, null, 2));
          actions.setSubmitting(false);
        }, 1000);
      }}
      render={props =&gt; (
        <form>
          <input value="{props.values.name}" type="text">
          {props.errors.name &amp;&amp; <div id="feedback">{props.errors.name}</div>}
          <button type="submit">Submit</button>
        </form>
      )}
    /&gt;
  </div>
);

Formik render methods

There are three ways to render things with ``

• ``
• ``
• ``

Formik props

All three render methods will be passed the same props:

dirty: boolean

Returns true if any field has been touched by any means, false otherwise. dirty is a readonly computed property and should not be mutated directly.

errors: { [field: string]: string }

Form validation errors. Should match the shape of your form's [values] defined in initialValues. If you are using [validationSchema] (which you should be), keys and shape will match your schema exactly. Internally, Formik transforms raw Yup validation errors on your behalf. If you are using [validate], then that function will determine the errors objects shape.

handleBlur: (e: any) => void

onBlur event handler. Useful for when you need to track whether an input has been [touched] or not. This should be passed to <input>

DOM-only. Use [setFieldTouched] in React Native.

handleChange: (e: React.ChangeEvent) => void

General input change event handler. This will update the values[key] where key is the event-emitting input's name attribute. If the name attribute is not present, handleChange will look for an input's id attribute. Note: "input" here means all HTML inputs.

DOM-only. Use [setFieldValue] in React Native.

handleReset: () => void

Reset handler. Will reset the form to its initial state. This should be passed to <button>...</button>

handleSubmit: (e: React.FormEvent) => void

Submit handler. This should be passed to <form>...</form>

isSubmitting: boolean

Submitting state. Either true or false. Formik will set this to true on your behalf before calling [handleSubmit] to reduce boilerplate.

isValid: boolean

Returns true if the there are no [errors], or the result of [isInitialValid] the form if is in "pristine" condition (i.e. not [dirty])).

resetForm: (nextValues?: Values) => void

Imperatively reset the form. This will clear [errors] and [touched], set [isSubmitting] to false and rerun mapPropsToValues with the current WrappedComponent's props or what's passed as an argument. That latter is useful for calling resetForm within componentWillReceiveProps.

setErrors: (fields: { [field: string]: string }) => void

Set errors imperatively.

setFieldError: (field: string, errorMsg: string) => void

Set the error message of a field imperatively. field should match the key of [errors] you wish to update. Useful for creating custom input error handlers.

setFieldTouched: (field: string, isTouched: boolean) => void

Set the touched state of a field imperatively. field should match the key of [touched] you wish to update. Useful for creating custom input blur handlers.

setFieldValue: (field: string, value: any) => void

Set the value of a field imperatively. field should match the key of [values] you wish to update. Useful for creating custom input change handlers.

setStatus: (status?: any) => void

Set a top-level [status] to anything you want imperatively. Useful for controlling arbitrary top-level state related to your form. For example, you can use it to pass API responses back into your component in [handleSubmit].

setSubmitting: (boolean) => void

Set [isSubmitting] imperatively.

setTouched: (fields: { [field: string]: boolean }) => void

Set [touched] imperatively.

setValues: (fields: { [field: string]: any }) => void

Set [values] imperatively.

status?: any

A top-level status object that you can use to represent form state that can't otherwised be expressed/stored with other methods. This is useful for capturing and passing through API responses to your inner component.

status should only be modifed by calling setStatus: (status?: any) => void

touched: { [field: string]: boolean }

Touched fields. Each key corresponds to a field that has been touched/visited.

values: { [field: string]: any }

Your form's values. Will have the shape of the result of [mapPropsToValues] (if specified) or all props that are not functions passed to your wrapped component.

component

;

const ContactForm = ({
  handleSubmit,
  handleChange,
  handleBlur,
  values,
  errors,
}) => (
  <form>
    <input value="{values.name}" type="text">
    {errors.name &amp;&amp; <div>{errors.name}</div>}
    <button type="submit">Submit</button>
  </form>
};

Warning: takes precendence over so don’t use both in the same ``.

render: (props: FormikProps) => ReactNode

 }/>

 (
    <form>
      <input value="{values.name}" type="text">
      {errors.name &amp;&amp;
        <div>
          {errors.name}
        </div>}
      <button type="submit">Submit</button>
    </form>
  )}
/&gt;

children: func

 }/>

// or...


  {({ handleSubmit, handleChange, handleBlur, values, errors }) => (
    <form>
      <input value="{values.name}" type="text">
      {errors.name &amp;&amp;
        <div>
          {errors.name}
        </div>}
      <button type="submit">Submit</button>
    </form>
  )}

enableReinitialize?: boolean

Default is false. Control whether Formik should reset the form if [initialValues] changes (using deep equality).

isInitialValid?: boolean

Default is false. Control the initial value of [isValid] prop prior to mount. You can also pass a function. Useful for situations when you want to enable/disable a submit and reset buttons on initial mount.

initialValues?: Values

Initial field values of the form, Formik will make these values available to render methods component as [props.values][values].

Even if your form is empty by default, you must initialize all fields with initial values otherwise React will throw an error saying that you have changed an input from uncontrolled to controlled.

Note: initialValues not available to the higher-order component, use [mapPropsToValues] instead.

onSubmit: (values: Values, formikBag: FormikBag) => void

Your form submission handler. It is passed your forms [values] and the "FormikBag", which includes an object containing a subset of the injected props and methods (i.e. all the methods with names that start with set + resetForm) and any props that were passed to the the wrapped component.

Note: [errors], [touched], [status] and all event handlers are NOT included in the FormikBag.

validate?: (values: Values) => FormikError | Promise

Note: I suggest using [validationSchema] and Yup for validation. However, validate is a dependency-free, straightforward way to validate your forms.

Validate the form's [values] with function. This function can either be:

1. Synchronous and return an [errors] object.

// Synchronous validation
const validate = (values, props) => {
  let errors = {};

  if (!values.email) {
    errors.email = 'Required';
  } else if (!/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i.test(values.email)) {
    errors.email = 'Invalid email address';
  }

  //...

  return errors;
};

• Asynchronous and return a Promise that's error is an [errors] object

// Async Validation
const sleep = ms => new Promise(resolve => setTimeout(resolve, ms))

const validate = (values, props) => {
  return sleep(2000).then(() => {
    let errors = {}
    if (['admin', 'null', 'god']).includes(values.username) {
      errors.username = 'Nice try'
    }
    // ...
    if (Object.keys(errors).length) {
      throw errors
    }
  })
}

validateOnBlur?: boolean

Default is true. Use this option to run validations on blur events. More specifically, when either [handleBlur], [setFieldTouched], or [setTouched] are called.

validateOnChange?: boolean

Default is true. Use this option to tell Formik to run validations on change events and change-related methods. More specifically, when either [handleChange], [setFieldValue], or [setValues] are called.

validationSchema?: Schema | (() => Schema)

A Yup schema or a function that returns a Yup schema. This is used for validation. Errors are mapped by key to the inner component's [errors]. Its keys should match those of [values].

``

will automagically hook up inputs to Formik. It uses the `name` attribute to match up with Formik state. will default to an <input> element. To change the underlying element of , specify a `component` prop. It can either be a string like `select` or another React component. can also take a render prop.

import  React from 'react';
import { Formik, Field } from 'formik';

const Example = () => (
  <div>
    <h1>My Form</h1>
     {
        setTimeout(() =&gt; {
          alert(JSON.stringify(values, null, 2))
          actions.setSubmitting(false)
        }, 1000);
      }}
      render={(props: FormikProps) =&gt;
        <form>
          
          
            <option value="red">Red</option>
            <option value="green">Green</option>
            <option value="blue">Blue</option>
          
          
          
             <input>
          } /&gt;
          <button type="submit">Submit</button>
        }
    /&gt;
  </form></div>
);

const CustomInputComponent: React.SFC &amp; CustomInputProps&gt; =&gt; ({
  field, // { name, value, onChange, onBlur }
  form: { touched, errors }, // also values, setXXXX, handleXXXX, dirty, isValid, status, etc.
  ...props
}) =&gt; (
  <div>
    <input type="text">
    {touched[field.name] &amp;&amp; errors[field.name] &amp;&amp; <div>{errors[field.name]}</div>}
  </div>
)

<form>

Like , is a helper component you can use to save time. It is tiny wrapper around . This means you don't need to explictly type out if you don't want to.

ReactDOM only

import React from 'react';
import { Formik, Field, Form } from 'formik';

const Example = () => (
  <div>
    <h1>My Form</h1>
     {
        setTimeout(() =&gt; {
          alert(JSON.stringify(values, null, 2));
          actions.setSubmitting(false);
        }, 1000);
      }}
      component={MyForm}
    /&gt;
  </div>
);

const MyForm = () =&gt; (
  
    
    
      <option value="red">Red</option>
      <option value="green">Green</option>
      <option value="blue">Blue</option>
    
    <button type="submit">Submit</button>
  
);

withFormik(options)

Create a higher-order React component class that passes props and form handlers (the "FormikBag") into your component derived from supplied options.

options

displayName?: string

When your inner form component is a stateless functional component, you can use the displayName option to give the component a proper name so you can more easily find it in React DevTools. If specified, your wrapped form will show up as Formik(displayName). If omitted, it will show up as Formik(Component). This option is not required for class components (e.g. class XXXXX extends React.Component {..}).

enableReinitialize?: boolean

Default is false. Control whether Formik should reset the form if the wrapped component props change (using deep equality).

handleSubmit: (values: Values, formikBag: FormikBag) => void

Your form submission handler. It is passed your forms [values] and the "FormikBag", which includes an object containing a subset of the injected props and methods (i.e. all the methods with names that start with set + resetForm) and any props that were passed to the the wrapped component.

The "FormikBag":

• props (props passed to the wrapped component)
• [resetForm]
• [setErrors]
• [setFieldError]
• [setFieldTouched]
• [setFieldValue]
• [setStatus]
• [setSubmitting]
• [setTouched]
• [setValues]

Note: [errors], [touched], [status] and all event handlers are NOT included in the FormikBag.

isInitialValid?: boolean | (props: Props) => boolean

Default is false. Control the initial value of [isValid] prop prior to mount. You can also pass a function. Useful for situations when you want to enable/disable a submit and reset buttons on initial mount.

mapPropsToValues?: (props: Props) => Values

If this option is specified, then Formik will transfer its results into updatable form state and make these values available to the new component as [props.values][values]. If mapPropsToValues is not specified, then Formik will map all props that are not functions to the inner component's [props.values][values]. That is, if you omit it, Formik will only pass props where typeof props[k] !== 'function', where k is some key.

Even if your form is not receiving any props from its parent, use mapPropsToValues to initialize your forms empty state.

validate?: (values: Values, props: Props) => FormikError | Promise

Note: I suggest using [validationSchema] and Yup for validation. However, validate is a dependency-free, straightforward way to validate your forms.

Validate the form's [values] with function. This function can either be:

1. Synchronous and return an [errors] object.

// Synchronous validation
const validate = (values, props) => {
  let errors = {};

  if (!values.email) {
    errors.email = 'Required';
  } else if (!/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i.test(values.email)) {
    errors.email = 'Invalid email address';
  }

  //...

  return errors;
};

• Asynchronous and return a Promise that's error is an [errors] object

// Async Validation
const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));

const validate = (values, props) => {
  return sleep(2000).then(() => {
    let errors = {};
    if (['admin', 'null', 'god'].includes(values.username)) {
      errors.username = 'Nice try';
    }
    // ...
    if (Object.keys(errors).length) {
      throw errors;
    }
  });
};

validateOnBlur?: boolean

Default is true. Use this option to run validations on blur events. More specifically, when either [handleBlur], [setFieldTouched], or [setTouched] are called.

validateOnChange?: boolean

Default is true. Use this option to tell Formik to run validations on change events and change-related methods. More specifically, when either [handleChange], [setFieldValue], or [setValues] are called.

validationSchema?: Schema | ((props: Props) => Schema)

A Yup schema or a function that returns a Yup schema. This is used for validation. Errors are mapped by key to the inner component's [errors]. Its keys should match those of [values].

Injected props and methods

These are identical to the props of ...} />

Guides

React Native

Formik is 100% compatible with React Native and React Native Web. However, because of differences between ReactDOM's and React Native's handling of forms and text input, there are two differences to be aware of. This section will walk you through them and what I consider to be best practices.

Before going any further, here's a super minimal gist of how to use Formik with React Native that demonstrates the key differences:

// Formik x React Native example
import React from 'react';
import { Button, TextInput, View } from 'react-native';
import { withFormik } from 'formik';

const enhancer = withFormik({
  /*...*/
});

const MyReactNativeForm = props => (
  </form></form></form>