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:
- Getting values in and out of form state
- Validation and error messages
- 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.
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.
By now, you might be thinking, "Why didn't you just use Redux-Form?" Good question.
- According to our prophet Dan Abramov, form state is inherently emphemeral and local, so tracking it in Redux is unecessary
- Redux-Form calls your entire top-level reducer multiple times ON EVERY KEYSTROKE. This is fine for small apps, but as your Redux app grows, input latency will continue increase if you use Redux-Form
- I no longer use Redux or MobX, just React's setState.
- 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.
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.
Add Formik to your project.
npm i formik --save
You can also try before you buy with this demo of Formik on CodeSandbox.io
- 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
- An Introduction to Formik by Jared Palmer @ Spotify NYC. August 15th, 2017.
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<Formik />
: A React component with arender
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, handleSubmit, isSubmitting }) =>
<form onSubmit={handleSubmit}>
<input
type="email"
name="email"
onChange={handleChange}
value={values.email}
/>
{touched.email && errors.email && <div>{errors.email}</div>}
<input
type="password"
name="password"
onChange={handleChange}
value={values.password}
/>
{touched.password && errors.password && <div>{errors.password}</div>}
<button type="submit" disabled={isSubmitting}>Submit</button>
</form>
// Wrap our form with the using withFormik HoC
const MyForm = withFormik({
// Transform outer props into form values
mapPropsToValues: props => ({ email: '', password: '' }),
// Add a custom validation function (this can be async too!)
validate: (values, props) => {
let errors = {}
if (!values.email) {
errors.email = 'Required'
} else if (!/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i.test(values.email)) {
errors.email = 'Invalid email address'
}
return errors
},
// Submission handler
handleSubmit: (values, { props, setSubmitting, setErrors, /* setValues, setStatus, and other goodies */ }) => {
LoginToMyApp(values)
.then(
user => {
setSubmitting(false)
// do whatevs...
// props.updateUser(user)
},
errors => {
setSubmitting(false)
// Maybe even transform your API's errors into the same shape as Formik's!
setErrors(transformMyApiErrors(errors))
}
)
}
})(InnerForm)
// Use <MyForm /> anywhere
const Basic = () =>
<div>
<h1>My Form</h1>
<p>This can be anywhere in your application</p>
<MyForm />
</div>
export default Basic
// Render Prop
import React from 'react'
import { Formik } from 'formik'
const Basic = () =>
<div>
<h1>My Form</h1>
<p>This can be anywhere in your application</p>
{/*
The benefit of the render prop approach is that you have full access to React's
state, props, and composition model. Thus there is no need to map outer props
to values...you can just set the initial values, and if they depend on props / state
then--boom--you can directly access to props / state.
The render prop accepts your inner form component, which you can define separately or inline
totally up to you:
- `<Formik render={props => <form>...</form>}>`
- `<Formik component={InnerForm}>`
- `<Formik>{props => <form>...</form>}</Formik>` (identical to as render, just written differently)
*/}
<Formik
initialValues={{
email: '',
password: ''
}}
validate={values => {
// same as above, but feel free to move this into a class method now.
let errors = {}
if (!values.email) {
errors.email = 'Required'
} else if (!/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i.test(values.email)) {
errors.email = 'Invalid email address'
}
return errors
}}
onSubmit={(values, { setSubmitting, setErrors, /* setValues and other goodies */ }) => {
LoginToMyApp(values)
.then(
user => {
setSubmitting(false)
// do whatevs...
// props.updateUser(user)
},
errors => {
setSubmitting(false)
// Maybe transform your API's errors into the same shape as Formik's
setErrors(transformMyApiErrors(errors))
}
)
}}
render={({ values, errors, touched, handleChange, handleSubmit, isSubmitting }) =>
<form onSubmit={handleSubmit}>
<input
type="email"
name="email"
onChange={handleChange}
value={values.email}
/>
{touched.email && errors.email && <div>{errors.email}</div>}
<input
type="password"
name="password"
onChange={handleChange}
value={values.password}
/>
{touched.password && errors.password && <div>{errors.password}</div>}
<button type="submit" disabled={isSubmitting}>Submit</button>
</form>}
/>
</div>
export default Basic
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 โค๏ธ 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
- API
<Formik />
- Formik render methods
- Formik props
dirty: boolean
errors: { [field: string]: string }
handleBlur: (e: any) => void
handleChange: (e: React.ChangeEvent<any>) => void
handleReset: () => void
handleSubmit: (e: React.FormEvent<HTMLFormEvent>) => 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<Values>) => ReactNode
children: func
enableReinitialize?: boolean
isInitialValid?: boolean
initialValues?: Values
onSubmit: (values: Values, formikBag: FormikBag) => void
validate?: (values: Values) => FormikError<Values> | Promise<any>
validateOnBlur?: boolean
validateOnChange?: boolean
validationSchema?: Schema | (() => Schema)
<Field />
<Form />
withFormik(options)
options
displayName?: string
enableReinitialize?: boolean
handleSubmit: (values: Values, formikBag: FormikBag) => void
isInitialValid?: boolean | (props: Props) => boolean
mapPropsToValues?: (props: Props) => Values
validate?: (values: Values, props: Props) => FormikError<Values> | Promise<any>
validateOnBlur?: boolean
validateOnChange?: boolean
validationSchema?: Schema | ((props: Props) => Schema)
- Injected props and methods
- Guides
- Organizations and projects using Formik
- Authors
- Contributors
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 onClose={onClose}>
<h1>Edit User</h1>
<Formik
initialValues={{ email, ...social }}
onSubmit={(values, actions) => {
CallMyApi(user.id, values)
.then(
updatedUser => {
actions.setSubmitting(false)
updateUser(updatedUser),
onClose()
},
error => {
actions.setSubmitting(false)
actions.setErrors(transformMyAPIErrorToAnObject(error));
}
)
}}
render={({ values, errors, touched, handleBlur, handleChange, handleSubmit, isSubmitting }) =>
<form onSubmit={handleSubmit}>
<input
type="email"
name="email"
onChange={handleChange}
value={values.email}
/>
{errors.email &&
touched.email &&
<div>
{errors.email}
</div>}
<input
type="text"
name="facebook"
onChange={handleChange}
value={values.facebook}
/>
{errors.facebook &&
touched.facebook &&
<div>
{errors.facebook}
</div>}
<input
type="text"
name="twitter"
onChange={handleChange}
value={values.twitter}
/>
{errors.twitter &&
touched.twitter &&
<div>
{errors.twitter}
</div>}
<button type="submit" disabled={isSubmitting}>
Submit
</button>
</form>}
/>
</Dialog>
)
}
To make writing forms less verbose. Formik comes with a few helpers to save you key strokes.
<Field>
<Form/>
This is the exact same form as before, but written with <Form/>
and <Field/>
:
// 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 onClose={onClose}>
<h1>Edit User</h1>
<Formik
initialValues={{ email, ...social }}
onSubmit={(values, actions) => {
CallMyApi(user.id, values)
.then(
updatedUser => {
actions.setSubmitting(false)
updateUser(updatedUser),
onClose()
},
error => {
actions.setSubmitting(false)
actions.setErrors(transformMyAPIErrorToAnObject(error));
}
)
}}
render={({ errors, touched, isSubmitting }) =>
<Form>
<Field type="email" name="email" />
{errors.email &&
touched.email &&
<div>
{errors.email}
</div>}
<Field type="text" name="facebook" />
{errors.facebook &&
touched.facebook &&
<div>
{errors.facebook}
</div>}
<Field type="text" name="twitter" />
{errors.twitter &&
touched.twitter &&
<div>
{errors.twitter}
</div>}
<button type="submit" disabled={isSubmitting}>
Submit
</button>
</Form>}
/>
</Dialog>
)
}
<Formik>
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>
<Formik
initialValues={{ name: 'jared' }}
onSubmit={(values, actions) => {
setTimeout(() => {
alert(JSON.stringify(values, null, 2))
actions.setSubmitting(false)
}, 1000);
}}
render={(props) =>
<form onSubmit={props.handleSubmit}>
<input
type="text"
onChange={props.handleChange}
onBlur={props.handleBlur}
value={props.values.name}
name="name"
/>
{props.errors.name &&
<div id="feedback">
{props.errors.name}
</div>}
<button type="submit">Submit</button>
</form>}
/>
</div>;
There are three ways to render things with <Formik/>
<Formik component>
<Formik render>
<Formik children>
All three render methods will be passed the same props:
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.
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.
onBlur
event handler. Useful for when you need to track whether an input has been touched
or not. This should be passed to <input onBlur={handleBlur} ... />
DOM-only. Use setFieldTouched
in React Native.
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.
Reset handler. Will reset the form to its initial state. This should be passed to <button onClick={handleReset}>...</button>
Submit handler. This should be passed to <form onSubmit={props.handleSubmit}>...</form>
Submitting state. Either true
or false
. Formik will set this to true
on your behalf before calling handleSubmit
to reduce boilerplate.
Returns true
if the there are no errors
, or the result of isInitialValid
the form if is in "pristine" condition (i.e. not dirty
)).
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
.
Set errors
imperatively.
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.
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.
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.
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
.
Set isSubmitting
imperatively.
Set touched
imperatively.
Set values
imperatively.
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 fields. Each key corresponds to a field that has been touched/visited.
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.
<Formik component={ContactForm} />
const ContactForm = ({ handleSubmit, handleChange, handleBlur, values, errors }) => {
return
<form onSubmit={handleSubmit}>
<input
type="text"
onChange={handleChange}
onBlur={handleBlur}
value={values.name}
name="name"
/>
{errors.name &&
<div>
{errors.name}
</div>}
<button type="submit">Submit</button>
</form>
}
Warning: <Formik component>
takes precendence over <Formik render>
so donโt use both in the same <Formik>
.
<Formik render={props => <ContactForm {...props} />}/>
<Formik
render={({ handleSubmit, handleChange, handleBlur, values, errors }) => (
<form onSubmit={handleSubmit}>
<input
type="text"
onChange={handleChange}
onBlur={handleBlur}
value={values.name}
name="name"
/>
{errors.name &&
<div>
{errors.name}
</div>}
<button type="submit">Submit</button>
</form>
)}
/>
<Formik children={props => <ContactForm {...props} />}/>
// or...
<Formik>
{({ handleSubmit, handleChange, handleBlur, values, errors }) => (
<form onSubmit={handleSubmit}>
<input
type="text"
onChange={handleChange}
onBlur={handleBlur}
value={values.name}
name="name"
/>
{errors.name &&
<div>
{errors.name}
</div>}
<button type="submit">Submit</button>
</form>
)}
</Formik>
Default is false
. Control whether Formik should reset the form if [initialValues
] changes (using deep equality).
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.
Initial field values of the form, Formik will make these values available to render methods component as props.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.
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<Thing>
+ 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
.
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:
- 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
}
})
}
Default is true
. Use this option to run validations on blur
events. More specifically, when either handleBlur
, setFieldTouched
, or setTouched
are called.
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.
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
.
<Field />
will automagically hook up inputs to Formik. It uses the name
attribute to match up with Formik state. <Field/>
will default to and <input/>
element. To change the underlying element of <Field/>
, specify a component
prop. It can either be a string like select
or another React component.
import React from 'react';
import { Formik, Field } from 'formik';
const Example = () => (
<div>
<h1>My Form</h1>
<Formik
initialValues={{ email: '', color: 'red', firstName: '' }}
onSubmit={(values, actions) => {
setTimeout(() => {
alert(JSON.stringify(values, null, 2))
actions.setSubmitting(false)
}, 1000);
}}
render={(props: FormikProps<Values>) =>
<form onSubmit={props.handleSubmit}>
<Field type="email" name="email" placeholder="Email" />
<Field component="select" name="color" >
<option value="red">Red</option>
<option value="green">Green</option>
<option value="blue">Blue</option>
</Field>
<Field component={CustomInputComponent} name="firstName" />
<button type="submit">Submit</button>
</form>}
/>
</div>
);
const CustomInputComponent: React.SFC<FormikProps<Values> & CustomInputProps> => ({
field, // { name, value, onChange, onBlur }
form: { touched, errors } // also values, setXXXX, handleXXXX, isDirty, isValid, status, etc.
...props
}) => (
<div>
<input
type="text"
{...field}
{...props}
/>
{touched[name] && errors[name] && <div className="error">{errors[name]}</div>}
</div>
)
Like <Field/>
, <Form/>
is a helper component you can use to save time. It is tiny wrapper around <form onSubmit={context.formik.handleSubmit} />
. This means you don't need to explictly type out <form onSubmit={props.handleSubmit}/>
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>
<Formik
initialValues={{ email: '', color: 'red' }}
onSubmit={(values, actions) => {
setTimeout(() => {
alert(JSON.stringify(values, null, 2))
actions.setSubmitting(false)
}, 1000);
}}
component={MyForm}
/>
</div>
);
const MyForm = () =>
<Form>
<Field type="email" name="email" placeholder="Email" />
<Field component="select" name="color">
<option value="red">Red</option>
<option value="green">Green</option>
<option value="blue">Blue</option>
</Field>
<button type="submit">Submit</button>
</Form>;
Create a higher-order React component class that passes props and form handlers (the "FormikBag
") into your component derived from supplied options.
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 {..}
).
Default is false
. Control whether Formik should reset the form if the wrapped component props change (using deep equality).
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<Thing>
+ resetForm
) and any props that were passed to the the wrapped component.
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
.
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.
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
. If mapPropsToValues
is not specified, then Formik will map all props that are not functions to the inner component's props.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.
Note: I suggest using [validateSchema
] 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:
- 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;
}
});
};
Default is true
. Use this option to run validations on blur
events. More specifically, when either handleBlur
, setFieldTouched
, or setTouched
are called.
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.
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
.
These are identical to the props of <Formik render={props => ...} />
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 =>
<View>
<TextInput
onChangeText={text => props.setFieldValue('email', text)}
value={props.values.email}
/>
<Button onPress={props.handleSubmit} title="Submit" /> //
</View>;
export default enhancer(MyReactNativeForm);
As you can see above, the notable differences between using Formik with React DOM and React Native are:
- Formik's
props.handleSubmit
is passed to a<Button onPress={...}/>
instead of HTML<form onSubmit={...}/>
component (since there is no<form/>
element in React Native). <TextInput />
uses Formik'sprops.setFieldValue
instead ofprops.handleChange
. To understand why, see the discussion below.
'cuz handleChange
will not work in React Native...
import { Button, TextInput, View } from 'react-native';
import { Formik } from 'formik';
const MyReactNativeForm = props => (
<View>
<Formik
onSubmit={(values, actions) => {
setTimeout(() => {
console.log(JSON.stringify(values, null, 2))
actions.setSubmitting(false)
}, 1000);
}}
render={props =>
<View>
<TextInput
name="email"
onChangeText={props.handleChange} // this WILL NOT WORK IN RN
value={props.values.email}
/>
<Button onPress={props.handleSubmit} />
</View>
}
/>
</View>
)
The reason is that Formik's handleChange
function expects its first argument to be synthetic DOM event where the event.target
is the DOM input element and event.target.id
or event.target.name
matches the field to be updated. Without this, handleChange
will do nothing.
In React Native, neither <TextInput />
's onChange
nor onChangeText
callbacks pass such an event or one like it to its callback. Instead, they do the following (emphasis added):
onChange?: function
Callback that is called when the text input's text changes.
onChangeText?: function
Callback that is called when the text input's text changes. Changed text is passed as an argument to the callback handler.
However, Formik works just fine if you use props.setFieldValue
! Philisophically, just treat React Native's <TextInput/>
the same way you would any other 3rd party custom input element.
In conclusion, the following WILL work in React Native:
// ...
// this works.
export const MyReactNativeForm = props =>
<View>
<TextInput
onChangeText={text => props.setFieldValue('email', text)}
value={props.values.email}
/>
<Button onPress={props.handleSubmit} />
</View>;
// ...
If you are like me and do not like render callbacks, I suggest treating React Native's <TextInput/>
as if it were another 3rd party custom input element:
- Write your own class wrapper around the custom input element
- Pass the custom component
props.setFieldValue
instead ofprops.handleChange
- Use a custom change handler callback that calls whatever you passed-in
setFieldValue
as (in this case we'll match the React Native TextInput API and call itthis.props.onChangeText
for parity).
// FormikReactNativeTextInput.js
import * as React from 'react'
import { TextInput } from 'react-native'
export default class FormikReactNativeTextInput extends React.Component {
handleChange = (value: string) => {
// remember that onChangeText will be Formik's setFieldValue
this.props.onChangeText(this.props.name, value)
}
render() {
// we want to pass through all the props except for onChangeText
const { onChangeText, ...otherProps } = this.props
return (
<TextInput
onChangeText={this.handleChange}
{...otherProps} // IRL, you should be more explicit when using TS
/>
);
}
}
Then you could just use this custom input as follows:
// MyReactNativeForm.js
import { View, Button } from 'react-native'
import { FormikReactNativeTextInput as TextInput } from './FormikReactNativeTextInput'
import { Formik } from 'formik'
const MyReactNativeForm = props => (
<View>
<Formik
onSubmit={(values, actions) => {
setTimeout(() => {
console.log(JSON.stringify(values, null, 2))
actions.setSubmitting(false)
}, 1000);
}}
render={props =>
<View>
<TextInput
name="email"
onChangeText={props.setFieldValue}
value={props.values.email}
/>
<Button onPress={props.handleSubmit} />
</View>
}
/>
</View>
)
export default MyReactNativeForm
List of organizations and projects using Formik
- Jared Palmer @jaredpalmer
- Ian White @eonwhite
Formik is made with <3 thanks to these wonderful people (emoji key):
This project follows the all-contributors specification. Contributions of any kind welcome!
MIT License.