# `UnLocode`

A place in trade and transport: a country's code and three letters or digits, `GBLON`.

Use it for ports, freight terminals and other places in shipping documents. For an airport, use [`IataAirport`](/docs/types/type-iata-airport.md). For a street address, use [`PostalAddress`](/docs/types/type-postal-address.md).

## Shape

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

## Example

```jadpo
UnLocode("GBLON")
```

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

`text.parse(raw, as: UnLocode)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `GB LON`, `gblon` or `UKLON`.

## Good to know

- Write it with no space and in capitals. `text.format` shows `GB LON`, the way it is usually printed.
- `==` 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
"GBLON"
"USNYC"
"DEHAM"
```

## Details

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

`UnLocode` is in the group Places, 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: `GBLON`, `USNYC` and `DEHAM`.

### How it is stored

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

### How it is shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `GBLON` | `GB LON` |
| `USNYC` | `US NYC` |
| `DEHAM` | `DE HAM` |

### 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>