# Forms

Redwood provides several helpers to make building forms easier. All of Redwood's helpers are simple wrappers around React Hook Form (RHF) that make it even easier to use in most cases.

If Redwood's helpers aren't flexible enough for you, you can use React Hook Form directly. @redwoodjs/forms exports everything it does:

import { 
  useForm, 
  useFormContext, 
  /**
   * Or anything else React Hook Form exports!
   * 
   * @see {@link https://react-hook-form.com/api}
   */
} from '@redwoodjs/forms'

# Overview

@redwoodjs/forms exports the following components:

Component	Description
`<Form>`	Surrounds all components, providing form and error contexts
`<FormError>`	Displays error messages from the server. Typically placed at the top of your form
`<Label>`	Used in place of the HTML `<label>` tag. Accepts error-styling props
`<InputField>`	Used in place of the HTML `<input>` tag. Accepts validation and error-styling props (also see the list of input field components enumerated below)
`<SelectField>`	Used in place of the HTML `<select>` tag. Accepts validation and error-styling props
`<TextAreaField>`	Used in place of the HTML `<textarea>` tag. Accepts validation and error-styling props
`<FieldError>`	Displays error messages if the field with the same `name` prop has validation errors. Only renders if there's an error on the associated field
`<Submit>`	Used in place of `<button type="submit">`. Triggers validation and "submission" (executes the function passed to `<Form>`'s `onSubmit` prop)

All HTML <input> types are also available as components. They follow the naming convention <TypeField> where Type is one of the HTML input types. We'll refer to them collectively as "input fields". The full list is:

<ButtonField>
<CheckboxField>
<ColorField>
<DateField>
<DatetimeLocalField>
<EmailField>
<FileField>
<HiddenField>
<ImageField>
<MonthField>
<NumberField>
<PasswordField>
<RadioField>
<RangeField>
<ResetField>
<SearchField>
<SubmitField>
<TelField>
<TextField>
<TimeField>
<UrlField>
<WeekField>

# Validation and Error-styling Props

All components ending in Field (i.e. all input fields, along with <SelectField> and <TextAreaField>) accept validation and error-styling props. By validation and error-styling props, we mean three props specifically:

validation, which accepts all of React Hook Form's register options, plus the Redwood-exclusive coercion helpers valueAsBoolean, valueAsJSON
errorClassName and errorStyle, which are the classes and styles to apply if there's an error

Besides name, all other props passed to these components are forwarded to the tag they render. Here's a table for reference:

Prop	Description
`name`	The name of the field. React Hook Form uses it a key to hook it up with everything else
`validation`	All your validation logic. Accepts all of React Hook Form's `register` options, plus the Redwood-exclusive coercion helpers `valueAsBoolean`, `valueAsJSON`
`errorClassName`	The class name to apply if there's an error
`errorStyle`	The style to apply if there's an error

# Example

A typical React component using these helpers would look something like this:

import {
  Form,
  Label,
  TextField,
  TextAreaField,
  FieldError,
  Submit,
} from '@redwoodjs/forms'

const ContactPage = () => {
  const onSubmit = (data) => {
    console.log(data)
  }

  return (
    <Form onSubmit={onSubmit}>
      <Label name="name" className="label" errorClassName="label error" />
      <TextField
        name="name"
        className="input"
        errorClassName="input error"
        validation={{ required: true }}
      />
      <FieldError name="name" className="error-message" />

      <Label name="email" className="label" errorClassName="label error" />
      <TextField
        name="email"
        className="input"
        errorClassName="input error"
        validation={{
          required: true,
          pattern: {
            value: /[^@]+@[^\.]+\..+/,
          },
        }}
      />
      <FieldError name="email" className="error-message" />

      <Label name="message" className="label" errorClassName="label error" />
      <TextAreaField
        name="message"
        className="input"
        errorClassName="input error"
        validation={{ required: true }}
      />
      <FieldError name="message" className="error-message" />

      <Submit className="button">Save</Submit>
    </Form>
  )
}

# `<Form>`

Any form you want Redwood to validate and style in the presence errors should be surrounded by this tag.

Prop	Description
`config`	Accepts an object containing options for React Hook Form's `useForm` hook
`formMethods`	The functions returned from `useForm`. You only need to use this prop if you need to access to one of the functions that `useForm` returns (see example below)
`onSubmit`	Accepts a function to be called if validation succeeds. Called with an object containing name-value pairs of all the fields in your form

All other props are forwarded to the <form> tag that it renders.

# `<Form>` Explained

<Form> encapsulates React Hook Form's useForm hook and <FormProvider> context, along with Redwood's ServerError context. It's hard to talk about this component without getting into the nitty-gritty of React Hook Forms.

useForm is React Hook Form's major hook. It returns a bunch of functions, one of which is register, which you use to quite literally "register" fields into React Hook Form so it can validate them. (This has to do with controlled vs. uncontrolled components. React Hook Form takes the latter approach.)

All of Redwood's form helpers need the register function to do what they do. But they don't get it straight from <Form> because they could be nested arbitrarily deep. That's where <FormProvider> comes in: by passing the functions returned from useForm to <FormProvider>, Redwood's helpers can just use useFormContext to get what they need.

# Using `formMethods`

There's some functions that useForm returns that it'd be nice to have access to. For example, useForm returns a function reset, which resets the form's fields. To access it, you have to call useForm yourself. But you still need to pass useForm's return to the <FormProvider> so that Redwood's helpers can register themselves:

import { useForm } from 'react-hook-form'

const ContactPage = () => {
  const formMethods = useForm()

  const onSubmit = (data) => {
    console.log(data)
    formMethods.reset()
  }

  return (
    <Form formMethods={formMethods} onSubmit={onSubmit}>
      // Still works!
      <TextField name="name" validation={{ required: true }}>
    </Form>
  )
}

# `<FormError>`

This helper renders a <div> containing a "title" message and a <ul> enumerating any errors reported by the server when trying to save your form. You can see it in a scaffold if you submit a form that somehow gets passed client-side validation:

For example, let's say you have a form with a <TextField> for a user's email address, but you didn't specify any validation on it:

import { useMutation } from '@redwoodjs/web'

const CREATE_CONTACT = gql`
  mutation CreateContactMutation($input: ContactInput!) {
    createContact(input: $input) {
      id
    }
  }
`

const ContactPage = () => {
  const [create, { loading, error }] = useMutation(CREATE_CONTACT)

  const onSubmit = (data) => {
    create({ variables: { input: data }})
  }

  return (
    <Form onSubmit={onSubmit}>
      <FormError error={error}>
      // No validation—any email goes!
      <TextField name="email" />    </Form>
  )
}

Since there's no validation, anything goes! On the client at least. GraphQL is built on types, so it's not going to let just anything through. Instead it'll throw an error and bubble it back up to the top (via the error object returned by the useMutation hook) where <FormError> can render something like:

<div>
  <p>
    Can't create new contact:
  </p>
  <ul>
    <li>
      email is not formatted like an email address
    </li>
  </ul>
</div>

# `<Label>`

Renders an HTML <label> tag with different className and style props depending on whether the field it's associated with has a validation error.

This tag can be self-closing, in which case the name becomes the text of the label:

<Label name="name" className="input" errorClassName="input error" />

<!-- Renders: <label for="name" class="input">name</label> -->

It can also have standard separate open/close tags and take text inside, in which case that text is the text of the rendered <label>:

<Label name="name" className="input" errorClassName="input error">Your Name</Label>

<!-- Renders: <label for="name" class="input">Your Name</label> -->

All props are passed to the underlying <label> tag besides the ones listed below:

Prop	Description
`name`	The name of the field that this label is associated with. This should be the same as the `name` prop on the input field this label is for
`errorClassName`	The `className` that's used if the field with the same `name` has a validation error
`errorStyle`	The `style` that's used if the field with the same `name` has a validation error

# Input Fields

Inputs are the backbone of most forms. While you can use <InputField> and it's type prop to make all the different kinds of input fields you'd use in a form, it's often easier to reach for the named input fields (listed above) which have defaults for things like coercion configured where appropriate.

# Default coercion

Certain input fields handle coercion automatically, but you can always override the coercion or, if it's not built-in, set it manually via the validation prop's setValueAs property.

The input fields that coerce automatically are:

Field	Default coercion
`<CheckboxField>`	`valueAsBoolean`
`<NumberField>`	`valueAsNumber`
`<DateField>`	`valueAsDate`
`<DatetimeLocalField>`	`valueAsDate`

valueAsDate and valueAsNumber are built into React Hook Form and are based on the HTML standard. But because Redwood uses GraphQL on the backend, it's important that the types submitted by the form be what the GraphQL server expects. Instead of forcing users to make heavy-use of setValueAs for custom coercion, Redwood extends react hook form's valueAs properties with two more for convenience:

valueAsBoolean
valueAsJSON

Another nice thing Redwood does for you is automatically treat empty strings ('') as undefined for text input fields whose name ends in Id to make it easier to work with fields for optional database relations. You can disable this by marking the field required, by supplying your own setValueAs function, or by simply renaming the field.

# `<SelectField>`

Renders an HTML <select> tag. It's possible to select multiple values using the multiple prop. When multiple is true, this field returns an array of values in the same order as the list of options, not in the order they were selected.

<SelectField name="toppings" multiple={true}>
  <option>'lettuce'</option>
  <option>'tomato'</option>
  <option>'pickle'</option>
  <option>'cheese'</option>
</SelectField>  

// If the user chooses lettuce, tomato, and cheese, 
// the onSubmit handler receives: 
// 
// { toppings: ["lettuce", "tomato", "cheese"] }
//

# Validation

In these two examples, one with multiple-field selection, validation requires that a field be selected and that the user doesn't select the first value in the dropdown menu:

<SelectField
  name="selectSingle"
  validation={{
    required: true,
    validate: {
      matchesInitialValue: (value) => {
        return (
          value !== 'Please select an option' ||
          'Select an Option'
        )
      },
    },
  }}
>
  <option>Please select an option</option>
  <option>Option 1</option>
  <option>Option 2</option>
</SelectField>
<FieldError name="selectSingle" style={{ color: 'red' }} />

<SelectField
  multiple={true}  name="selectMultiple"
  validation={{
    required: true,
    validate: {
      matchesInitialValue: (value) => {
        let returnValue = [true]
        returnValue = value.map((element) => {
          if (element === 'Please select an option')
            return 'Select an Option'
        })
        return returnValue[0]
      },
    },
  }}
>
  <option>Please select an option</option>
  <option>Option 1</option>
  <option>Option 2</option>
</SelectField>
<FieldError name="selectMultiple" style={{ color: 'red' }} />

# Coercion

Typically, a <SelectField> returns a string, but you can use one of the valueAs properties to return another type. An example use-case is when <SelectField> is being used to select a numeric identifier. Without the valueAsNumber property, <SelectField> returns a string. But, as per the example below, the valueAsNumber can be used to return an Int:

<SelectField name="select" validation={{ valueAsNumber: true }}>
  <option value={1}>Option 1</option>
  <option value={2}>Option 2</option>
  <option value={3}>Option 3</option>
</SelectField>

If Option 3 is selected, the <Form>'s onSubmit function is passed data as follows:

{
  select: 3,
}

As with input fields, Redwood will automatically treat empty strings ('') as undefined for select fields whose name ends in Id. See the previous section about this for more info.

# `<FieldError>`

Renders a <span> containing a validation error message if the field with the same name attribute has a validation error. Otherwise renders nothing.

<FieldError name="name" className="error-message">

<!-- Renders: <span class="error-message">name is required</span> -->

RedwoodJS

中国镜像

# Forms

# Overview

# Validation and Error-styling Props

# Example

# `<Form>`

# `<Form>` Explained

# Using `formMethods`

# `<FormError>`

# `<Label>`

# Input Fields

# Default coercion

# `<SelectField>`

# Validation

# Coercion

# `<FieldError>`

# Forms

# Overview

# Validation and Error-styling Props

# Example

# <Form>

# <Form> Explained

# Using formMethods

# <FormError>

# <Label>

# Input Fields

# Default coercion

# <SelectField>

# Validation

# Coercion

# <FieldError>

# `<Form>`

# `<Form>` Explained

# Using `formMethods`

# `<FormError>`

# `<Label>`

# `<SelectField>`

# `<FieldError>`