# `UsSsn`

A US Social Security number, nine digits that the SSA could have issued: `123456789`. Shown to people as its last four only, `•••-••-6789`. Personal data.

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

## Make one

Build one from its text, `UsSsn("123456789")`, which checks it: text that isn't one breaks `format`.

`text.parse(raw, as: UsSsn)` reads one from its text; text that isn't one at all fails `malformed`, such as `000123456`, `666123456` or `900123456`.

## 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 |
|---|---|
| `123456789` | `"123456789"` |
| `001010001` | `"001010001"` |

It is stored in one column named for the field, of type `text`. `001010001` is stored as `'001010001'`.

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `123456789` | `•••-••-6789` |
| `001010001` | `•••-••-0001` |

## 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.