# `UnNumber`

A dangerous good's UN number (the UN Model Regulations): `UN1203`, printed `UN 1203`.

[Other with a published standard](types.md#other-with-a-published-standard); not ordered; since Jadpo 0.1.0.

## Make one

Build one from its text, `UnNumber("UN1203")`, which checks it: text that isn't one breaks `format`.

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

## Text, JSON and storage

`text.from` writes its canonical text, the one form `text.parse` reads back. JSON sends its canonical text as a string.

| Text | JSON |
|---|---|
| `UN1203` | `"UN1203"` |
| `UN3480` | `"UN3480"` |

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

## 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 has the contract's own operations: `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. It isn't ordered, so `<` and sorting don't take it. [Every standard type meets one contract](../topics/every-standard-type-meets-one-contract.md) says how they work.