# `InterestRateBasis`

What an interest rate is quoted as: `aer`, `apr` or `flat`.

Use it as part of an [`InterestRate`](/docs/types/type-interest-rate.md), which most apps want instead. `aer` is for savings, `apr` for borrowing, and `flat` is a rate on the sum first lent.

## Shape

One of these 3 values:

`InterestRateBasis.aer`, `InterestRateBasis.apr`, `InterestRateBasis.flat`.

## Example

```jadpo
InterestRateBasis.apr
```

`text.parse(raw, as: InterestRateBasis)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `apy`, `annual` or `a p r`.

## Good to know

- `==` 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
"aer"
"apr"
"flat"
```

## Details

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

`InterestRateBasis` is in the group Money and banking, 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: `aer`, `apr` and `flat`.

### How it is stored

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

### How it is shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `aer` | `AER` |
| `apr` | `APR` |
| `flat` | `flat` |

### 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>