# `NhsNumber`

An NHS number, the patient identifier in England, Wales and the Isle of Man: ten digits.

Use it to identify a patient. Write it with no spaces. `text.format` adds them: `943 476 5919`. For a condition or a diagnosis, use [`Icd10Code`](/docs/types/type-icd10-code.md) or [`SnomedConcept`](/docs/types/type-snomed-concept.md).

## Shape

One value, held as text in one set form, with no parts: `9990000018`.

## Example

```jadpo
NhsNumber("9434765919")
```

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

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

## Good to know

- It checks its own last digit, so a mistyped number is usually refused.
- `==` tells you whether two are the same. `<` and `list.sort_by` don't take it.
- A field that holds one counts as personal data (`health`), so you don't mark it yourself.

## In JSON

A string, in a request, a response or `json.write`:

```json
"9434765919"
"9990000018"
```

## Details

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

`NhsNumber` is in the group Tax and identity numbers, 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: `9434765919` and `9990000018`.

### How it is stored

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

### How it is 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 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>