# `Hostname`

A host (RFC 3986): a domain name, or an IP address as `IpAddress` writes it, an IPv6 address without brackets.

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

## Make one

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

`text.parse(raw, as: Hostname)` reads one from its text; text that isn't one at all fails `malformed`, such as `Example.com`, `[2001:db8::1]` or `2001:DB8::1`.

## 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"` |
| `localhost` | `"localhost"` |
| `192.0.2.1` | `"192.0.2.1"` |
| `2001:db8::1` | `"2001:db8::1"` |

It is stored in one column named for the field, of type `text`. `192.0.2.1` is stored as `'192.0.2.1'`.

## 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` |
| `localhost` | `localhost` |
| `192.0.2.1` | `192.0.2.1` |
| `2001:db8::1` | `2001:db8::1` |

## 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.