# `PhoneExtension`

An internal extension dialled after a phone number: up to 20 digits.

Use it beside a [`PhoneNumber`](/docs/types/type-phone-number.md) for an office line's extension. The main number goes in the [`PhoneNumber`](/docs/types/type-phone-number.md).

## Shape

One value, held as text in one set form, with no parts: `2047`.

## Example

```jadpo
PhoneExtension("2047")
```

`PhoneExtension(raw)` checks the text, and text that isn't one breaks the `format` rule.

`text.parse(raw, as: PhoneExtension)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `x2047`, `20 47` or `123456789012345678901`.

## Good to know

- It holds digits only: leave out any `x` or "ext".
- `==` tells you whether two are the same. `<` and `list.sort_by` don't take it.
- A field that holds one counts as personal data (`contact`), so you don't mark it yourself.

## In JSON

A string, in a request, a response or `json.write`:

```json
"1"
"2047"
```

## Details

<details>
<summary>Text form, storage, how it is shown, and operations</summary>

`PhoneExtension` is in the group People and contact, and has been in Jadpo since 0.1.0.

### Text form

`text.from` writes one standard text form, the same form `text.parse` reads back: `1` and `2047`.

### How it is stored

It is stored in one column named for the field, of type `text`. `2047` is stored as `'2047'`.

### How it is shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `1` | `1` |
| `2047` | `2047` |

### Operations

It also takes `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. [How every standard type behaves](/docs/every-standard-type-meets-one-contract.md) says how they work.

</details>