<!--
This file was generated by Spark. Do not edit it by hand.
-->
# GuardedStruct.Derive.Extension


## derives
Container for custom validator and sanitizer ops.

#### Example

defmodule MyApp.Derives do
use GuardedStruct.Derive.Extension

derives do
validator :slug, fn input ->
is_binary(input) and Regex.match?(~r/^[a-z0-9-]+$/, input)
end

sanitizer :slugify, fn input when is_binary(input) ->
input |> String.downcase() |> String.replace(~r/[^a-z0-9-]+/u, "-")
end
end
end


### Nested DSLs
 * [validator](#derives-validator)
 * [sanitizer](#derives-sanitizer)


### derives.validator
```elixir
validator name, fun
```


Declare a custom validator op callable as `validate(<name>)` from
any GuardedStruct module that has this extension wired in.


### Arguments

| Name | Type | Default | Docs |
|------|------|---------|------|
| [`name`](#derives-validator-name){: #derives-validator-name .spark-required} | `atom` |  | Op name. Used as `validate(<name>)` in derive strings. |
| [`fun`](#derives-validator-fun){: #derives-validator-fun .spark-required} | `any` |  | Single-arg function. Return value semantics:   * `true` — input passes   * `false` — input fails (default error message)   * `{:error, field, action, message}` — explicit error   * any other value — used as the validated (coerced) output |


### derives.sanitizer
```elixir
sanitizer name, fun
```


Declare a custom sanitizer op callable as `sanitize(<name>)`. Runs
before validation in the derive pipeline; the return value replaces
the input.


### Arguments

| Name | Type | Default | Docs |
|------|------|---------|------|
| [`name`](#derives-sanitizer-name){: #derives-sanitizer-name .spark-required} | `atom` |  | Op name. Used as `sanitize(<name>)` in derive strings. |
| [`fun`](#derives-sanitizer-fun){: #derives-sanitizer-fun .spark-required} | `any` |  | Single-arg function. Return value replaces the input. |


<style type="text/css">.spark-required::after { content: "*"; color: red !important; }</style>