# Contrak
**Schema and contract validation library for Elixir**
[](https://github.com/bluzky/contrak/actions) [](https://coveralls.io/github/bluzky/contrak?branch=main) [](https://hex.pm/packages/contrak) [](https://hexdocs.pm/contrak/)
## Installation
Adding `contrak` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:contrak, "~> 0.1.1"}
]
end
```
Documentation here [https://hexdocs.pm/contrak](https://hexdocs.pm/contrak).
## Usage
`Contrak` helps to validate data with given schema:
```elixir
task_schema = %{
title: [type: :string, required: true, length: [min: 20]],
description: :string,
tag: [type: {:array, :string}, default: []]
point: [type: :integer, number: [min: 0]],
due_date: [type: NaiveDateTime, default: &seven_day_from_now/0] ,
assignee: [type: {:array, User}, required: true],
attachments: [
type: %{
name: [type: :string, required: true],
url: :string
}
]
}
case Contrak.validate(data, task_schema) do
{:ok, valid_data} ->
# do your logic
{:error, errors} ->
IO.inspect(errors)
end
```
`Contrak` also do:
- Support nested type
- Clean not allowed fields
**NOTES: Contract only validate data, not cast data**
## Schema definition
`Contrak` provide a simple schema definition:
`<field_name>: [type: <type>, required: <true|false>, default: <value|function>, [...validation]]`
```elixir
%{
product_name: [type: :string, required: true, length: [min: 20]],
sku: [type: :string, required: true],
selling_price: [type: :integer, required: true, number: [min: 0]]
state: [type: :string, default: "draft"]
}
```
Shorthand form if you only check for type:
`<field_name>: <type>`
```elixir
%{
product_name: :string,
sku: :string,
price: :integer
}
```
- `type` is all types supported by `Valdi.validate_type`, and extended to support nested type.
Nested type is just another schema.
- `default`: could be a function `func/0` or a value. Default function is invoked for every time `validate` is called.
If not set, default value is `nil`
- `required`: if set to `true`, validate if a field does exist and not `nil`. Default is `false`.
- `validations`: all validation support by `Valdi`, if value is `nil` then all validation is skip
For more details, please check document for [Contrak.Schema](https://hexdocs.pm/contrak/Contrak.Schema.html)
## Validations
`Contrak` uses [Valdi](https://github.com/bluzky/valdi) to validate data. So you can use all validation from `Valdi`. This is list of available validation for current version of Valdi:
- Validate type
- Validate required
- Validate `in`|`not_in` enum
- Valiate length for `string`, `enumerable`
- Validate number
- Validate string against regex pattern
- Custom validation function
Please check [Valdi document](https://hexdocs.pm/valdi/readme.html) for more details
