# `DomainName`

A domain name (IDNA 2008 by UTS 46), lower case, each label beyond ASCII as its A-label, with no dot at the end: `xn--mnchen-3ya.de`. Every domain name is a `Hostname`.

[Web and network](types.md#web-and-network); not ordered; since Jadpo 0.1.0.

## Make one

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

`text.parse(raw, as: DomainName)` reads one from its text; text that isn't one at all fails `malformed`, such as `Example.com`, `example.com.` or `-example.com`.

## 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 |
|---|---|
| `example.com` | `"example.com"` |
| `www.example.co.uk` | `"www.example.co.uk"` |
| `xn--mnchen-3ya.de` | `"xn--mnchen-3ya.de"` |
| `localhost` | `"localhost"` |

It is stored in one column named for the field, of type `text`. `xn--mnchen-3ya.de` is stored as `'xn--mnchen-3ya.de'`.

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `example.com` | `example.com` |
| `www.example.co.uk` | `www.example.co.uk` |
| `xn--mnchen-3ya.de` | `xn--mnchen-3ya.de` |
| `localhost` | `localhost` |

## 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.