# `TraceId`

A trace's id (W3C Trace Context): 32 lower-case hexadecimal digits, not all zero.

[Software](types.md#software); not ordered; since Jadpo 0.1.0.

## Make one

Build one from its text, `TraceId("4bf92f3577b34da6a3ce929d0e0e4736")`, which checks it: text that isn't one breaks `format`.

`text.parse(raw, as: TraceId)` reads one from its text; text that isn't one at all fails `malformed`, such as `00000000000000000000000000000000`, `4BF92F3577B34DA6A3CE929D0E0E4736` or `4bf92f3577b34da6a3ce929d0e0e473`.

## 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 |
|---|---|
| `4bf92f3577b34da6a3ce929d0e0e4736` | `"4bf92f3577b34da6a3ce929d0e0e4736"` |
| `0af7651916cd43dd8448eb211c80319c` | `"0af7651916cd43dd8448eb211c80319c"` |

It is stored in one column named for the field, of type `text`. `0af7651916cd43dd8448eb211c80319c` is stored as `'0af7651916cd43dd8448eb211c80319c'`.

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `4bf92f3577b34da6a3ce929d0e0e4736` | `4bf92f3577b34da6a3ce929d0e0e4736` |
| `0af7651916cd43dd8448eb211c80319c` | `0af7651916cd43dd8448eb211c80319c` |

## 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.