Gazebo_simulation-Frontend/node_modules/react-admin/docs/Fields.md

---
layout: default
title: "Field Components"
---

# Field Components

A `Field` component displays a given property of a REST resource. Such components are used in the `List` view, but you can also use them in the `Edit` and `Create` views for read-only fields. The most usual of all field components is `<TextField>`:

```jsx
// in src/posts.js
import React from 'react';
import { List, Datagrid, TextField } from 'react-admin';

export const PostList = (props) => (
    <List {...props}>
        <Datagrid>
            <TextField source="id" />
            <TextField source="title" />
            <TextField source="body" />
        </Datagrid>
    </List>
);
```

All field components accept the following attributes:

* `source`: Property name of your entity to view/edit. This attribute is required.
* `label`: Used as a table header of an input label. Defaults to the `source` when omitted.
* `sortable`: Should the list be sortable using `source` attribute? Defaults to `true`.
* `className`: A class name (usually generated by JSS) to customize the look and feel of the field element itself
* `cellClassName`: A class name (usually generated by JSS) to customize the look and feel of the field container (e.g. the `<td>` in a `Datagrid`).
* `headerClassName`: A class name (usually generated by JSS) to customize the look and feel of the field header (e.g. the `<th>` in a `Datagrid`).
* `addLabel`: Defines the visibility of the label when the field is not in a `Datagrid`. Default value is `true`.
* `textAlign`: Defines the text alignment inside a cell. Supports `left` (the default) and `right`.

{% raw %}
```jsx
<TextField source="zb_title" label="Title" style={{ color: 'purple' }} />
```
{% endraw %}

**Tip**: You can use field components inside the `Edit` or `Show` views, too:

```jsx
export const PostShow = ({ ...props }) => (
    <Show {...props}>
        <SimpleShowLayout>
            <TextField source="title" />
        </SimpleShowLayout>
    </Show>
);
```

**Tip**: If you display a record with a complex structure, you can use a path with dot separators as the `source` attribute. For instance, if the API returns the following 'book' record:

```js
{
    id: 1234,
    title: 'War and Peace',
    author: {
        firstName: 'Leo',
        lastName: 'Tolstoi'
    }
}
```

Then you can display the author first name as follows:

```jsx
<TextField source="author.firstName" />
```

**Tip**: If you want to format a field according to the value, use a higher-order component to do conditional formatting, as described in the [Theming documentation](./Theming.md#conditional-formatting).

**Tip**: If your interface has to support multiple languages, don't use the `label` prop, and put the localized labels in a dictionary instead. See the [Translation documentation](./Translation.md#translating-resource-and-field-names) for details.

## `<ArrayField>`

Display a collection using `<Field>` child components.

Ideal for embedded arrays of objects, e.g. `tags` and `backlinks` in the following `post` object:

```js
{
  id: 123,
  tags: [
        { name: 'foo' },
        { name: 'bar' }
  ],
  backlinks: [
        {
            date: '2012-08-10T00:00:00.000Z',
            url: 'http://example.com/foo/bar.html',
        },
        {
            date: '2012-08-14T00:00:00.000Z',
            url: 'https://blog.johndoe.com/2012/08/12/foobar.html',
        }
   ]
}
```

The child must be an iterator component (like `<Datagrid>` or `<SingleFieldList>`).

Here is how to display all the backlinks of the current post as a `<Datagrid>`

```jsx
<ArrayField source="backlinks">
    <Datagrid>
        <DateField source="date" />
        <UrlField source="url" />
    </Datagrid>
</ArrayField>
```

And here is how to display all the tags of the current post as `<Chip>` components:

```jsx
<ArrayField source="tags">
    <SingleFieldList>
        <ChipField source="name" />
    </SingleFieldList>
</ArrayField>
```

**Tip**: If you need to render a collection in a custom way, it's often simpler to write your own component:

```jsx
const TagsField = ({ record }) => (
    <ul>
        {record.tags.map(item => (
            <li key={item.name}>{item.name}</li>
        ))}
    </ul>
)
TagsField.defaultProps = { addLabel: true };
```

## `<BooleanField>`

Displays a boolean value as a check.

```jsx
import { BooleanField } from 'react-admin';

<BooleanField source="commentable" />
```

![BooleanField](./img/boolean-field.png)

The `BooleanField` also includes an hidden text for accessibility (or to query in end to end tests). By default, it includes the translated label and the translated value, for example `Published: false`.

If you need to override it, you can use the `valueLabelTrue` and `valueLabelFalse` props which both accept a string. Those strings may be translation keys:

```jsx
// Simple texts
<BooleanField source="published" valueLabelTrue="Has been published" valueLabelFalse="Has not been published yet" />

// Translation keys
<BooleanField source="published" valueLabelTrue="myapp.published.true" valueLabelFalse="myapp.published.false" />
```

## `<ChipField>`

Displays a value inside a ["Chip"](https://material-ui.com/components/chips), which is Material UI's term for a label.

```jsx
import { ChipField } from 'react-admin';

<ChipField source="category" />
```

![ChipField](./img/chip-field.png)

This field type is especially useful for one to many relationships, e.g. to display a list of books for a given author:

```jsx
import { ChipField, SingleFieldList, ReferenceManyField } from 'react-admin';

<ReferenceManyField reference="books" target="author_id">
    <SingleFieldList>
        <ChipField source="title" />
    </SingleFieldList>
</ReferenceManyField>
```

## `<DateField>`

Displays a date or datetime using the browser locale (thanks to `Date.toLocaleDateString()` and `Date.toLocaleString()`).

```jsx
import { DateField } from 'react-admin';

<DateField source="publication_date" />
```

This component accepts a `showTime` attribute (`false` by default) to force the display of time in addition to date. It uses `Intl.DateTimeFormat()` if available, passing the `locales` and `options` props as arguments. If Intl is not available, it ignores the `locales` and `options` props.

{% raw %}
```jsx
<DateField source="publication_date" />
// renders the record { id: 1234, publication_date: new Date('2017-04-23') } as
<span>4/23/2017</span>

<DateField source="publication_date" showTime />
// renders the record { id: 1234, publication_date: new Date('2017-04-23 23:05') } as
<span>4/23/2017, 11:05:00 PM</span>

<DateField source="publication_date" options={{ weekday: 'long', year: 'numeric', month: 'long', day: 'numeric' }} />
// renders the record { id: 1234, publication_date: new Date('2017-04-23') } as
<span>Sunday, April 23, 2017</span>

<DateField source="publication_date" locales="fr-FR" />
// renders the record { id: 1234, publication_date: new Date('2017-04-23') } as
<span>23/04/2017</span>

<DateField source="publication_date" elStyle={{ color: 'red' }} />
// renders the record { id: 1234, publication_date: new Date('2017-04-23') } as
<span style="color:red;">4/23/2017</span>
```
{% endraw %}

See [Intl.DateTimeformat documentation](https://developer.mozilla.org/fr/docs/Web/JavaScript/Reference/Objets_globaux/Date/toLocaleDateString) for the `options` prop syntax.

**Tip**: If you need more formatting options than what `Intl.DateTimeformat` can provide, build your own field component leveraging a third-party library like [moment.js](http://momentjs.com/).

## `<EmailField>`

`<EmailField>` displays an email as a `<a href="mailto:" />` link.

```jsx
import { EmailField } from 'react-admin';

<EmailField source="personal_email" />
```

## `<FunctionField>`

If you need a special function to render a field, `<FunctionField>` is the perfect match. It passes the `record` to a `render` function supplied by the developer. For instance, to display the full name of a `user` record based on `first_name` and `last_name` properties:

```jsx
import { FunctionField } from 'react-admin'

<FunctionField label="Name" render={record => `${record.first_name} ${record.last_name}`} />
```

**Tip**: Technically, you can omit the `source` and `sortBy` properties for the `<FunctionField>` since you provide the render function. However, providing a `source` or a `sortBy` will allow the `Datagrid` to make the column sortable, since when a user clicks on a column, the `Datagrid` uses these properties to sort. Should you provide both, `sortBy` will override `source` for sorting the column.

## `<ImageField>`

If you need to display an image provided by your API, you can use the `<ImageField />` component:

```jsx
import { ImageField } from 'react-admin';

<ImageField source="url" title="title" />
```

This field is also generally used within an [<ImageInput />](./Inputs.md#imageinput) component to display preview.

The optional `title` prop points to the picture title property, used for both `alt` and `title` attributes. It can either be an hard-written string, or a path within your JSON object:

```jsx
// { picture: { url: 'cover.jpg', title: 'Larry Cover (French pun intended)' } }

// Title would be "picture.title", hence "Larry Cover (French pun intended)"
<ImageField source="picture.url" title="picture.title" />

// Title would be "Picture", as "Picture" is not a path in previous given object
<ImageField source="picture.url" title="Picture" />
```

If passed value is an existing path within your JSON object, then it uses the object attribute. Otherwise, it considers its value as an hard-written title.


If the record actually contains an array of images in its property defined by the `source` prop, the `src` prop will be needed to determine the `src` value of the images, for example:

```js
// This is the record
{
    pictures: [
        { url: 'image1.jpg', desc: 'First image' },
        { url: 'image2.jpg', desc: 'Second image' },
    ],
}

<ImageField source="pictures" src="url" title="desc" />
```

## `<FileField>`

If you need to display a file provided by your API, you can use the `<FileField />` component:

```jsx
import { FileField } from 'react-admin';

<FileField source="url" title="title" />
```

This field is also generally used within an [<FileInput />](./Inputs.md#fileinput) component to display preview.

The optional `title` prop points to the file title property, used for `title` attributes. It can either be an hard-written string, or a path within your JSON object:

```jsx
// { file: { url: 'doc.pdf', title: 'Presentation' } }

// Title would be "file.title", hence "Presentation"
<FileField source="file.url" title="file.title" />

// Title would be "File", as "File" is not a path in previous given object
<FileField source="file.url" title="File" />
```

If passed value is an existing path within your JSON object, then it uses the object attribute. Otherwise, it considers its value as an hard-written title.

If the record actually contains an array of files in its property defined by the `source` prop, the `src` prop will be needed to determine the `href` value of the links, for example:

```js
// This is the record
{
    files: [
        { url: 'image1.jpg', desc: 'First image' },
        { url: 'image2.jpg', desc: 'Second image' },
    ],
}

<FileField source="files" src="url" title="desc" />
```

You can optionally set the `target` prop to choose which window will the link try to open in.

```jsx
// Will make the file open in new window
<FileField source="file.url" target="_blank" />
```

## `<NumberField>`

Displays a number formatted according to the browser locale, right aligned.

Uses `Intl.NumberFormat()` if available, passing the `locales` and `options` props as arguments. This allows perfect display of decimals, currencies, percentage, etc.

If Intl is not available, it outputs number as is (and ignores the `locales` and `options` props).

{% raw %}
```jsx
import { NumberField }  from 'react-admin';

<NumberField source="score" />
// renders the record { id: 1234, score: 567 } as
<span>567</span>

<NumberField source="score" options={{ maximumFractionDigits: 2 }}/>
// renders the record { id: 1234, score: 567.3567458569 } as
<span>567.35</span>

<NumberField source="share" options={{ style: 'percent' }} />
// renders the record { id: 1234, share: 0.2545 } as
<span>25%</span>

<NumberField source="price" options={{ style: 'currency', currency: 'USD' }} />
// renders the record { id: 1234, price: 25.99 } as
<span>$25.99</span>

<NumberField source="price" locales="fr-FR" options={{ style: 'currency', currency: 'USD' }} />
// renders the record { id: 1234, price: 25.99 } as
<span>25,99 $US</span>

<NumberField source="score" elStyle={{ color: 'red' }} />
// renders the record { id: 1234, score: 567 } as
<span style="color:red;">567</span>
```
{% endraw %}

See [Intl.Numberformat documentation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toLocaleString) for the `options` prop syntax.

**Tip**: If you need more formatting options than what `Intl.Numberformat` can provide, build your own field component leveraging a third-party library like [numeral.js](http://numeraljs.com/).

**Tip**: When used in a `Show` view, the right alignment may look weird. Disable it by resetting the `style` attribute:

{% raw %}
```jsx
import { NumberField }  from 'react-admin';

<NumberField source="score" style={{}} />
```
{% endraw %}

## `<SelectField>`

When you need to display an enumerated field, `<SelectField>` maps the value to a string.

For instance, if the `gender` field can take values "M" and "F", here is how to display it as "Male" or "Female":

```jsx
import { SelectField } from 'react-admin';

<SelectField source="gender" choices={[
   { id: 'M', name: 'Male' },
   { id: 'F', name: 'Female' },
]} />
```

By default, the text is built by

- finding a choice where the 'id' property equals the field value
- using the 'name' property an the option text

You can also customize the properties to use for the lookup value and text, thanks to the 'optionValue' and 'optionText' attributes.

```jsx
const choices = [
   { _id: 123, full_name: 'Leo Tolstoi', sex: 'M' },
   { _id: 456, full_name: 'Jane Austen', sex: 'F' },
];
<SelectField source="author_id" choices={choices} optionText="full_name" optionValue="_id" />
```

`optionText` also accepts a function, so you can shape the option text at will:

```jsx
const choices = [
   { id: 123, first_name: 'Leo', last_name: 'Tolstoi' },
   { id: 456, first_name: 'Jane', last_name: 'Austen' },
];
const optionRenderer = choice => `${choice.first_name} ${choice.last_name}`;
<SelectField source="author_id" choices={choices} optionText={optionRenderer} />
```

`optionText` also accepts a React Element, that will be cloned and receive the related choice as the `record` prop. You can use Field components there.

```jsx
const choices = [
   { id: 123, first_name: 'Leo', last_name: 'Tolstoi' },
   { id: 456, first_name: 'Jane', last_name: 'Austen' },
];
const FullNameField = ({ record }) => <Chip>{record.first_name} {record.last_name}</Chip>;
<SelectField source="author_id" choices={choices} optionText={<FullNameField />}/>
```

The current choice is translated by default, so you can use translation identifiers as choices:

```js
const choices = [
   { id: 'M', name: 'myroot.gender.male' },
   { id: 'F', name: 'myroot.gender.female' },
];
```

However, in some cases (e.g. inside a `<ReferenceField>`), you may not want the choice to be translated. In that case, set the `translateChoice` prop to `false`.

```jsx
<SelectField source="gender" choices={choices} translateChoice={false}/>
```

**Tip**: `<ReferenceField>` sets `translateChoice` to `false` by default.

## `<ReferenceField>`

This component fetches a single referenced record (using the `GET_MANY` REST method), and displays one field of this record. That's why a `<ReferenceField>` must always have a child `<Field>`.

For instance, here is how to fetch the `post` related to `comment` records, and display the `title` for each:

```jsx
import React from 'react';
import { List, Datagrid, ReferenceField, TextField } from 'react-admin';

export const PostList = (props) => (
    <List {...props}>
        <Datagrid>
            <TextField source="id" />
            <ReferenceField label="Author" source="user_id" reference="users">
                <TextField source="name" />
            </ReferenceField>
        </Datagrid>
    </List>
);
```

With this configuration, `<ReferenceField>` wraps the user's name in a link to the related user `<Edit>` page.

![ReferenceField](./img/reference-field.png)

`<ReferenceField>` accepts a `reference` attribute, which specifies the resource to fetch for the related record. Also, you can use any `Field` component as child.

**Note**: You **must** add a `<Resource>` for the reference resource - react-admin needs it to fetch the reference data. You *can* omit the `list` prop in this reference if you want to hide it in the sidebar menu.

```jsx
<Admin dataProvider={myDataProvider}>
    <Resource name="comments" list={CommentList} />
    <Resource name="posts" />
</Admin>
```

To change the link from the `<Edit>` page to the `<Show>` page, set the `link` prop to "show".

```jsx
<ReferenceField label="User" source="userId" reference="users" link="show">
    <TextField source="name" />
</ReferenceField>
```

By default, `<ReferenceField>` is sorted by its `source`. To specify another attribute to sort by, set the `sortBy` prop to the according attribute's name.

```jsx
<ReferenceField label="User" source="userId" reference="users" sortBy="user.name">
    <TextField source="name" />
</ReferenceField>
```

You can also prevent `<ReferenceField>` from adding link to children by setting `link` to `false`.

```jsx
// No link
<ReferenceField label="User" source="userId" reference="users" link={false}>
    <TextField source="name" />
</ReferenceField>
```

You can also use a custom `link` function to get a custom path for the children. This function must accept `record` and `reference` as arguments.

```jsx
// Custom path
<ReferenceField label="User" source="userId" reference="users" link={(record, reference) => `/my/path/to/${reference}/${record.id}`}>
    <TextField source="name" />
</ReferenceField>
```

**Tip**: React-admin accumulates and deduplicates the ids of the referenced records to make *one* `GET_MANY` call for the entire list, instead of n `GET_ONE` calls. So for instance, if the API returns the following list of comments:

```js
[
    {
        id: 123,
        body: 'Totally agree',
        post_id: 789,
    },
    {
        id: 124,
        title: 'You are right my friend',
        post_id: 789
    },
    {
        id: 125,
        title: 'Not sure about this one',
        post_id: 735
    }
]
```

Then react-admin renders the `<CommentList>` with a loader for the `<ReferenceField>`, fetches the API for the related posts in one call (`GET http://path.to.my.api/posts?ids=[789,735]`), and re-renders the list once the data arrives. This accelerates the rendering, and minimizes network load.

## `<ReferenceManyField>`

This component fetches a list of referenced records by reverse lookup of the current `record.id` in other resource (using the `GET_MANY_REFERENCE` REST method). You can specify the target field name, i.e. the field name of the current record's id in the other resource, using the required `target` field. The result is then passed to an iterator component (like `<SingleFieldList>` or `<Datagrid>`). The iterator component usually has one or more child `<Field>` components.

For instance, here is how to fetch the `comments` related to a `post` record by matching `comment.post_id` to `post.id`, and then display the `author.name` for each, in a `<ChipField>`:

```jsx
import React from 'react';
import { List, Datagrid, ChipField, ReferenceManyField, SingleFieldList, TextField } from 'react-admin';

export const PostList = (props) => (
    <List {...props}>
        <Datagrid>
            <TextField source="id" />
            <TextField source="title" type="email" />
            <ReferenceManyField label="Comments by" reference="comments" target="post_id">
                <SingleFieldList>
                    <ChipField source="author.name" />
                </SingleFieldList>
            </ReferenceManyField>
            <EditButton />
        </Datagrid>
    </List>
);
```

![ReferenceManyFieldSingleFieldList](./img/reference-many-field-single-field-list.png)

`<ReferenceManyField>` accepts a `reference` attribute, which specifies the resource to fetch for the related record. It also accepts a `source` attribute which define the field containing the value to look for in the `target` field of the referenced resource. By default this is the `id` of the resource (`post.id` in the previous example).

**Note**: You **must** add a `<Resource>` for the reference resource - react-admin needs it to fetch the reference data. You *can* omit the `list` prop in this reference if you want to hide it in the sidebar menu.

You can use a `<Datagrid>` instead of a `<SingleFieldList>` - but not inside another `<Datagrid>`! This is useful if you want to display a read-only list of related records. For instance, if you want to show the `comments` related to a `post` in the post's `<Edit>` view:

```jsx
import React from 'react';
import { Edit, Datagrid, SimpleForm, DateField, EditButton, ReferenceManyField, TextField, TextInput } from 'react-admin';

export const PostEdit = (props) => (
    <Edit {...props}>
        <SimpleForm>
            <TextInput disabled label="Id" source="id" />
            <TextInput source="title" />
            <ReferenceManyField
                label="Comments"
                reference="comments"
                target="post_id"
            >
                <Datagrid>
                    <DateField source="created_at" />
                    <TextField source="author.name" />
                    <TextField source="body" />
                    <EditButton />
                </Datagrid>
            </ReferenceManyField>
        </SimpleForm>
    </Edit>
);
```

![ReferenceManyFieldDatagrid](./img/reference-many-field-datagrid.png)

By default, react-admin restricts the possible values to 25 and displays no pagination control. You can change the limit by setting the `perPage` prop:

```jsx
<ReferenceManyField perPage={10} reference="comments" target="post_id">
   ...
</ReferenceManyField>
```

And if you want to allow users to paginate the list, pass a `<Pagination>` element as the `pagination` prop:

```jsx
import { Pagination } from 'react-admin';

<ReferenceManyField pagination={<Pagination />} reference="comments" target="post_id">
   ...
</ReferenceManyField>
```

By default, it orders the possible values by id desc. You can change this order by setting the `sort` prop (an object with `field` and `order` properties).

{% raw %}
```jsx
<ReferenceManyField sort={{ field: 'created_at', order: 'DESC' }} reference="comments" target="post_id">
   ...
</ReferenceManyField>
```
{% endraw %}

Also, you can filter the query used to populate the possible values. Use the `filter` prop for that.

{% raw %}
```jsx
<ReferenceManyField filter={{ is_published: true }} reference="comments" target="post_id">
   ...
</ReferenceManyField>
```
{% endraw %}

## `<ReferenceArrayField>`

Use `<ReferenceArrayField>` to display an list of reference values based on an array of foreign keys.

For instance, if a post has many tags, a post resource may look like:

```js
{
    id: 1234,
    title: 'Lorem Ipsum',
    tag_ids: [1, 23, 4]
}
```

Where `[1, 23, 4]` refer to ids of `tag` resources.

`<ReferenceArrayField>` can fetch the `tag` resources related to this `post` resource by matching `post.tag_ids` to `tag.id`. `<ReferenceArrayField source="tags_ids" reference="tags">` would issue an HTTP request looking like:

```
http://myapi.com/tags?id=[1,23,4]
```

**Tip**: `<ReferenceArrayField>` fetches the related resources using the `GET_MANY` REST method, so the actual HTTP request depends on your REST client.

Once it receives the related resources, `<ReferenceArrayField>` passes them to its child component using the `ids` and `data` props, so the child must be an iterator component (like `<SingleFieldList>` or `<Datagrid>`). The iterator component usually has one or more child `<Field>` components.

Here is how to fetch the list of tags for each post in a `PostList`, and display the `name` for each `tag` in a `<ChipField>`:

```jsx
import React from 'react';
import { List, Datagrid, ChipField, ReferenceArrayField, SingleFieldList, TextField } from 'react-admin';

export const PostList = (props) => (
    <List {...props}>
        <Datagrid>
            <TextField source="id" />
            <TextField source="title" />
            <ReferenceArrayField label="Tags" reference="tags" source="tag_ids">
                <SingleFieldList>
                    <ChipField source="name" />
                </SingleFieldList>
            </ReferenceArrayField>
            <EditButton />
        </Datagrid>
    </List>
);
```

**Note**: You **must** add a `<Resource>` component for the reference resource to your `<Admin>` component, because react-admin needs it to fetch the reference data. You can omit the `list` prop in this Resource if you don't want to show an entry for it in the sidebar menu.

```jsx
export const App = () => (
    <Admin dataProvider={restProvider('http://path.to.my.api')}>
        <Resource name="posts" list={PostList} />
        <Resource name="tags" /> // <= this one is compulsory
    </Admin>
);
```

In an Edit of Show view, you can combine `<ReferenceArrayField>` with `<Datagrid>` to display a related resources in a table. For instance, to display more details about the tags related to a post in the `PostShow` view:

```jsx
import React from 'react';
import { Show, SimpleShowLayout, TextField, ReferenceArrayField, Datagrid, ShowButton } from 'react-admin';

export const PostShow = (props) => (
    <Show {...props}>
        <SimpleShowLayout>
            <TextField source="id" />
            <TextField source="title" />
            <ReferenceArrayField label="Tags" reference="tags" source="tag_ids">
                <Datagrid>
                    <TextField source="id" />
                    <TextField source="name" />
                    <ShowButton />
                </Datagrid>
            </ReferenceArrayField>
            <EditButton />
        </SimpleShowLayout>
    </Show>
);
```

## `<RichTextField>`

This component displays some HTML content. The content is "rich" (i.e. unescaped) by default.

```jsx
import { RichTextField } from 'react-admin';

<RichTextField source="body" />
```

![RichTextField](./img/rich-text-field.png)

The `stripTags` attribute (`false` by default) allows you to remove any HTML markup, preventing some display glitches (which is especially useful in list views).

```jsx
import { RichTextField } from 'react-admin';

<RichTextField source="body" stripTags />
```

## `<TextField>`

The most simple as all fields, `<TextField>` simply displays the record property as plain text.

```jsx
import { TextField } from 'react-admin';

<TextField label="Author Name" source="name" />
```

## `<UrlField>`

`<UrlField>` displays an url in an `< a href="">` tag.

```jsx
import { UrlField } from 'react-admin';

<UrlField source="site_url" />
```

## Styling Fields

All field components accept a `className` prop, allowing you to customize their style to your liking. We advise you to use the Material UI styling solution, JSS, to generate those classes. See their [documentation](https://material-ui.com/customization/css-in-js/#api) about that.

```jsx
import { makeStyles } from '@material-ui/core/styles';

const useStyles = makeStyles({
    price: { color: 'purple' },
});

const PriceField = props => {
    const classes = useStyles();
    return <TextField className={classes.price} {...props} />;
};

export const ProductList = (props) => (
    <List {...props}>
        <Datagrid>
            <PriceField source="price" />
        </Datagrid>
    </List>
);

// renders in the Datagrid as
<td><span class="[class name generated by JSS]">2</span></td>
```

React-admin usually delegates the rendering of fields components to material-ui components. Refer to the material-ui documentation to see the default styles for elements.

You may want to customize the cell style inside a `DataGrid`. You can use the `cellClassName` for that:

{% raw %}
```jsx
import { makeStyles } from '@material-ui/core/styles';

const useStyles = makeStyles({
    priceCell: { fontWeight: 'bold' },
});

const PriceField = props => {
    const classes = useStyles();
    return <TextField cellClassName={classes.priceCell} {...props} />;
};

export const ProductList = (props) => (
    <List {...props}>
        <Datagrid>
            <PriceField source="price" />
        </Datagrid>
    </List>
);

// renders in the Datagrid as
<td class="[class name generated by JSS]"><span>2</span></td>
```
{% endraw %}

You may want to override the field header (the `<th>` element in the `Datagrid`). In that case, use the `headerClassName` prop:

{% raw %}
```jsx
import { makeStyles } from '@material-ui/core/styles';

const useStyles = makeStyles({
    priceHeader: { fontWeight: 'bold' },
});

const PriceField = props => {
    const classes = useStyles();
    return <TextField headerClassName={classes.priceHeader} {...props} />;
}

export const ProductList = (props) => (
    <List {...props}>
        <Datagrid>
            <PriceField source="price" />
        </Datagrid>
    </List>
);
// renders in the table header as
<th class="[class name generated by JSS]"><button>Price</button></td>
```
{% endraw %}

Finally, sometimes, you just want to right align the text of a cell. Use the `textAlign` prop, which accepts either `left` or `right`:

{% raw %}
```jsx
const PriceField = props => (
    <TextField {...props} />
);

PriceField.defaultProps = {
    textAlign: 'right',
};
```
{% endraw %}

## Writing Your Own Field Component

If you don't find what you need in the list above, you can write your own Field component. It must be a regular React component, accepting not only a `source` attribute, but also a `record` attribute. React-admin will inject the `record` based on the API response data at render time. The field component only needs to find the `source` in the `record` and display it.

For instance, here is an equivalent of react-admin's `<TextField>` component:

```jsx
import React from 'react';
import PropTypes from 'prop-types';

const TextField = ({ source, record = {} }) => <span>{record[source]}</span>;

TextField.propTypes = {
    label: PropTypes.string,
    record: PropTypes.object,
    source: PropTypes.string.isRequired,
};

export default TextField;
```

**Tip**: The `label` attribute isn't used in the `render()` method, but react-admin uses it to display the table header.

**Tip**: If you want to support deep field sources (e.g. source values like `author.name`), use [`lodash/get`](https://www.npmjs.com/package/lodash.get) to replace the simple object lookup:

```jsx
import get from 'lodash/get';
const TextField = ({ source, record = {} }) => <span>{get(record, source)}</span>;
```

If you are not looking for reusability, you can create even simpler components, with no attributes. Let's say an API returns user records with `firstName` and `lastName` properties, and that you want to display a full name in a user list.

```js
{
    id: 123,
    firstName: 'John',
    lastName: 'Doe'
}
```

The component will be:

```jsx
import React from 'react';
import { List, Datagrid, TextField } from 'react-admin';

const FullNameField = ({ record = {} }) => <span>{record.firstName} {record.lastName}</span>;
FullNameField.defaultProps = { label: 'Name' };

export const UserList = (props) => (
    <List {...props}>
        <Datagrid>
            <FullNameField source="lastName" />
        </Datagrid>
    </List>
);
```

**Tip**: In such custom fields, the `source` is optional. React-admin uses it to determine which column to use for sorting when the column header is clicked. In case you use the `source` property for additional purposes, the sorting can be overridden by the `sortBy` property on any `Field` component.

## Adding Label To Custom Field Components In The Show View

React-admin lets you use the same `Field` components in the `List` view and in the `Show` view. But if you use the `<FullNameField>` custom field component defined earlier in a `Show` view, something is missing: the `Field` label. Why do other fields have a label and not this custom `Field`? And how can you create a `Field` component that has a label in the `Show` view, but not in the `List` view?

React-admin uses a trick: the `Show` view layouts (`<SimpleShowLayout>` and `<TabbedShowLayout>`) inspect their `Field` children, and whenever one has the `addLabel` prop set to `true`, the layout adds a label.

That means that the only thing you need to add to a custom component to make it usable in a `Show` view is a `addLabel: true` default prop.

```js
FullNameField.defaultProps = {
    addLabel: true,
};
```

## Hiding A Field Based On The Value Of Another

In a Show view, you may want to display or hide fields based on the value of another field - for instance, show an `email` field only if the `hasEmail` boolean field is `true`.

For such cases, you can use the custom field approach: use the injected `record` prop, and render another Field based on the value.

```jsx
import React from 'react';
import { EmailField } from 'react-admin';

const ConditionalEmailField = ({ record, ...rest }) =>
    record && record.hasEmail
        ? <EmailField source="email" record={record} {...rest} />
        : null;

export default ConditionalEmailField;
```

**Tip**: Always check that the `record` is defined before inspecting its properties, as react-admin displays the `Show` view *before* fetching the record from the data provider. So the first time it renders the show view for a resource, the `record` is `undefined`.

This `ConditionalEmailField` is properly hidden when `hasEmail` is `false`. But when `hasEmail` is `true`, the Show layout renders it... without label. And if you add a `addLabel` default prop, the `Show` layout will render the label regardless of the `hasEmail` value...

One solution is to add the label manually in the custom component:

```jsx
import React from 'react';
import { Labeled, EmailField } from 'react-admin';

const ConditionalEmailField = ({ record, ...rest }) =>
    record && record.hasEmail
        ? (
            <Labeled label="Email">
                <EmailField source="email" record={record} {...rest} />
            </Labeled>
        )
        : null;

export default ConditionalEmailField;
```

This comes with a drawback, though: the `<ConditionalEmailField>` cannot be used in a List view anymore, as it will always have a label. If you want to reuse the custom component in a List, this isn't the right solution.

An alternative solution is to split the `<Show>` component. Under the hood, the `<Show>` component is composed of two sub components: the `<ShowController>` component, which fetches the record, and the `<ShowView>`, which is responsible for rendering the view title, actions, and children. `<ShowController>` uses the *render props* pattern:

```jsx
// inside react-admin
const Show = props => (
    <ShowController {...props}>
        {controllerProps => <ShowView {...props} {...controllerProps} />}
    </ShowController>
);
```

The `<ShowController>` fetches the `record` from the data provider, and passes it to its child function when received (among the `controllerProps`). That means the following code:

```jsx
import { Show, SimpleShowLayout, TextField } from 'react-admin';

const UserShow = props => (
    <Show {...props}>
        <SimpleShowLayout>
            <TextField source="username" />
            <TextField source="email" />
        </SimpleShowLayout>
    </Show>
);
```

Is equivalent to:

```jsx
import { ShowController, ShowView, SimpleShowLayout, TextField } from 'react-admin';

const UserShow = props => (
    <ShowController {...props}>
        {controllerProps =>
            <ShowView {...props} {...controllerProps}>
                <SimpleShowLayout>
                    <TextField source="username" />
                    <TextField source="email" />
                </SimpleShowLayout>
            </ShowView>
        }
    </ShowController>
);
```

If you want one field to be displayed based on the `record`, for instance to display the email field only if the `hasEmail` field is `true`, you just need to test the value from `controllerProps.record`, as follows:

```jsx
import { ShowController, ShowView, SimpleShowLayout, TextField } from 'react-admin';

const UserShow = props => (
    <ShowController {...props}>
        {controllerProps =>
            <ShowView {...props} {...controllerProps}>
                <SimpleShowLayout>
                    <TextField source="username" />
                    {controllerProps.record && controllerProps.record.hasEmail &&
                        <TextField source="email" />
                    }
                </SimpleShowLayout>
            </ShowView>
        }
    </ShowController>
);
```

And now you can use a regular Field component, and the label displays correctly in the Show view.