# Skema
Phoenix request params validation library.
[](https://github.com/bluzky/skema/actions) [](https://coveralls.io/github/bluzky/skema?branch=main) [](https://hex.pm/packages/skema) [](https://hexdocs.pm/skema/)
- [Skema](#skema)
- [Why Skema](#why-skema)
- [Installation](#installation)
- [Usage](#usage)
- [Define schema](#define-schema)
- [Default value](#default-value)
- [Custom cast function](#custom-cast-function)
- [1. Custom cast function accept value only](#1-custom-cast-fuction-accept-value-only)
- [2.Custom cast function accept tuple {M, f}](#3custom-cast-function-accept-tuple-m-f)
- [Nested schema](#nested-schema)
- [Validation](#validation)
- [Contributors](#contributors)
## Why Skema
- Reduce code boilerplate
- Shorter schema definition
- Default function which generate value each casting time
- Custom validation functions
- Custom parse functions
## Installation
[Available in Hex](https://hex.pm/skema), the package can be installed
by adding `skema` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:skema, "~> 0.1"}
]
end
```
## Usage
**Process order**
> Cast data -> validate casted data -> transform data
```elixir
use Skema
defschema IndexParams do
field :keyword, :string
field :status, :string, required: true
field :group_id, :integer, number: [greater_than: 0]
field :name, :string
end
def index(conn, params) do
with {:ok, better_params} <- Skema.cast(params, IndexParams) do
# do anything with your params
else
{:error, errors} -> # return params error
end
end
```
## Define schema
```elixir
use Skema
defschema IndexParams do
field :keyword, :string
field :status, :string, required: true
field :group_id, :integer, number: [greater_than: 0]
field :name, :string
end
```
Define a field using macro `@spec field(field_name :: atom(), type :: term(), opts \\ [])`
- `type`: `Skema` support same data type as `Ecto`. I borrowed code from Ecto
Supported options:
- `default`: default value or default function
- `cast_func`: custom cast function
- `number, format, length, in, not_in, func, required, each` are available validations
- `from`: use value from another field
- `as`: alias key you will receive from `Skema.cast` if casting is succeeded
### Default value
You can define a default value for a field if it's missing from the params.
```elixir
field :status, :string, default: "pending"
```
Or you can define a default value as a function. This function is evaluated when `Skema.cast` gets invoked.
```elixir
field :date, :utc_datetime, default: &Timex.now/0
```
### Custom cast function
You can define your own casting function, `skema` provide `cast_func` option.
Your `cast_func` must follows this spec
#### 1. Custom cast fuction accept value only
```elixir
fn(any) :: {:ok, any} | {:error, binary} | :error
```
```elixir
def my_array_parser(value) do
if is_binary(value) do
ids =
String.split(value, ",")
|> Enum.map(&String.to_integer(&1))
{:ok, ids}
else
{:error, "Invalid string"
end
end
defschema Sample do
field :user_id, {:array, :integer}, cast_func: &my_array_parser/1
end
```
This is a demo parser function.
### Nested schema
With `Skema` you can parse and validate nested map and list easily
```elixir
defschema Address do
field :street, :string
field :district, :string
field :city, :string
end
defschema User do
field :name, :string,
field :email, :string, required: true
field :addresses, {:array, Address}
end
```
## Validation
`Skema` uses `Valdi` validation library. You can read more about [Valdi here](https://github.com/bluzky/valdi)
Basically it supports following validation
- validate inclusion/exclusion
- validate length for string and enumerable types
- validate number
- validate string format/pattern
- validate custom function
- validate required(not nil) or not
- validate each array item
```elixir
defschema Product do
field :sku, :string, required: true, length: [min: 6, max: 20]
field :name, :string, required: true,
field :quantity, :integer, number: [min: 0],
field :type: :string, in: ~w(physical digital),
field :expiration_date, :naive_datetime, func: &my_validation_func/1,
field :tags, {:array, :string}, each: [length: [max: 50]]
end
```
### Dynamic required
- Can accept function or `{module, function}` tuple
- Only support 2 arity function
```elixir
def require_email?(value, data), do: is_nil(email.phone)
....
field :email, :string, required: {__MODULE__, :require_email?}
```
### Validate array item
Support validate array item with `:each` option, `each` accept a list of validators
```elixir
...
field :values, {:array, :number}, each: [number: [min: 20, max: 50]]
...
```
## Thank you
If you find a bug or want to improve something, please send a pull request. Thank you!
