# `ShoeSize`

A shoe size in its system, written as a box writes it: `UK 7.5`, `EU 42`.

[Commerce and logistics](types.md#commerce-and-logistics); not ordered; since Jadpo 0.1.0.

## Make one

Build one from its fields, `ShoeSize { system: ...  size: ... }`.

`text.parse(raw, as: ShoeSize)` reads one from its text; text that isn't one at all fails `malformed`, such as `UK 7,5`, `UK 7.25` or `UK 07`.

## Fields

| Field | Type |
|---|---|
| `system` | [`ShoeSizeSystem`](type-shoe-size-system.md) |
| `size` | `Text` |

## 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 |
|---|---|
| `UK 7.5` | `"UK 7.5"` |
| `EU 42` | `"EU 42"` |
| `US 9` | `"US 9"` |
| `EU 38.5` | `"EU 38.5"` |

It is stored in 2 columns, each named for the field, `_` and its suffix. This is `US 9`:

| Column | Type | Holds |
|---|---|---|
| `<field>_system` | `text` | `'US'` |
| `<field>_size` | `text` | `'9'` |

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `UK 7.5` | `UK 7.5` |
| `EU 42` | `EU 42` |
| `US 9` | `US 9` |
| `EU 38.5` | `EU 38.5` |

## 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.