# `UnNumber`

A dangerous good's UN number: `UN1203`.

Use it for hazardous goods on a shipping document.

## Shape

One value, held as text in one set form, with no parts: `UN3480`.

## Example

```jadpo
UnNumber("UN1203")
```

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

`text.parse(raw, as: UnNumber)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `1203`, `UN 1203` or `un1203`.

## Good to know

- Write it with no space. `text.format` adds one: `UN 1203`.
- `==` tells you whether two are the same. `<` and `list.sort_by` don't take it.

## In JSON

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

```json
"UN1203"
"UN3480"
```

## Details

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

`UnNumber` is in the group Other with a published standard, 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: `UN1203` and `UN3480`.

### How it is stored

It is stored in one column named for the field, of type `text`. `UN3480` is stored as `'UN3480'`.

### How it is shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `UN1203` | `UN 1203` |
| `UN3480` | `UN 3480` |

### 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>