# `NhsNumber`

An NHS number, ten digits with a mod-11 check digit: `9434765919`, shown to people as `943 476 5919`. Personal data.

[Tax and identity numbers](types.md#tax-and-identity-numbers); not ordered; personal data (health); since Jadpo 0.1.0.

## Make one

Build one from its text, `NhsNumber("9434765919")`, which checks it: text that isn't one breaks `format`.

`text.parse(raw, as: NhsNumber)` reads one from its text; text that isn't one at all fails `malformed`, such as `9434765918`, `1234567890` or `943 476 5919`.

## 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 |
|---|---|
| `9434765919` | `"9434765919"` |
| `9990000018` | `"9990000018"` |

It is stored in one column named for the field, of type `text`. `9990000018` is stored as `'9990000018'`.

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `9434765919` | `943 476 5919` |
| `9990000018` | `999 000 0018` |

## 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.