# `BloodType`

A person's blood group, ABO and RhD, written `O-`: health data.

[Health](types.md#health); not ordered; since Jadpo 0.1.0.

## Make one

Pick one of its variants, `BloodType.a_positive`.

`text.parse(raw, as: BloodType)` reads one from its text; text that isn't one at all fails `malformed`, such as `O pos`, `0+` or `O`.

## Variants

| Variant | Written |
|---|---|
| `a_positive` | `A+` |
| `a_negative` | `A-` |
| `ab_positive` | `AB+` |
| `ab_negative` | `AB-` |
| `b_positive` | `B+` |
| `b_negative` | `B-` |
| `o_positive` | `O+` |
| `o_negative` | `O-` |

## 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 |
|---|---|
| `AB+` | `"AB+"` |
| `O-` | `"O-"` |

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

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `AB+` | `AB+` |
| `O-` | `O-` |

## 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.