# `PostalCode`

A postal code or ZIP code, such as `SW1A 1AA`.

Use it on its own when you only need the code, such as for a delivery estimate. Inside a full address, it is a field of [`PostalAddress`](/docs/types/type-postal-address.md), which also checks it against the country.

## Shape

One value, held as text in one set form, with no parts: `100-8994`.

## Example

```jadpo
PostalCode("SW1A 1AA")
```

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

`text.parse(raw, as: PostalCode)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `sw1a 1aa`, ` SW1A 1AA` or `SW1A 1AA `.

## Good to know

- Built on its own, it knows no country, so it checks only the general form: capital letters, digits, spaces and `-`, up to 12 of them. Upper-case what a person types before you build one.
- `==` 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
"SW1A 1AA"
"22162-1010"
"100-8994"
```

## Details

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

`PostalCode` 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: `SW1A 1AA`, `22162-1010` and `100-8994`.

### How it is stored

It is stored in one column named for the field, of type `text`. `22162-1010` is stored as `'22162-1010'`.

### How it is shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `SW1A 1AA` | `SW1A 1AA` |
| `22162-1010` | `22162-1010` |
| `100-8994` | `100-8994` |

### 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>