# `HttpHeaderName`

An HTTP field name (RFC 9110), a token in lower case: `content-type`.

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

## Make one

Build one from its text, `HttpHeaderName("content-type")`, which checks it: text that isn't one breaks `format`.

`text.parse(raw, as: HttpHeaderName)` reads one from its text; text that isn't one at all fails `malformed`, such as `Content-Type`, `content type` or `content-type:`.

## 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 |
|---|---|
| `content-type` | `"content-type"` |
| `accept-language` | `"accept-language"` |
| `x-request-id` | `"x-request-id"` |

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

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `content-type` | `content-type` |
| `accept-language` | `accept-language` |
| `x-request-id` | `x-request-id` |

## 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.