# `SerialNumber`

One item's own serial number: up to 20 characters, such as `SN-0042a`.

Use it for individual items you may need to trace, such as a warranty. For a whole batch, use [`LotNumber`](/docs/types/type-lot-number.md). For a kind of product, use [`Sku`](/docs/types/type-sku.md).

## Shape

One value, held as text in one set form, with no parts: `SN-0042a`.

## Example

```jadpo
SerialNumber("SN-0042a")
```

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

`text.parse(raw, as: SerialNumber)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `SN 0042`, `SN#0042` or `123456789012345678901`.

## Good to know

- It can't contain spaces or `#`, since these are the characters GS1 barcodes take.
- `==` tells you whether two are the same. `<` and `list.sort_by` don't take it.

## In JSON

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

```json
"12345678"
"SN-0042a"
```

## Details

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

`SerialNumber` is in the group Commerce and logistics, 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: `12345678` and `SN-0042a`.

### How it is stored

It is stored in one column named for the field, of type `text`. `SN-0042a` is stored as `'SN-0042a'`.

### How it is shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `12345678` | `12345678` |
| `SN-0042a` | `SN-0042a` |

### 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>