Contrak

Schema and contract validation library for Elixir

This library is best suited for validating compicated params contract/schema passing to your function. For example when you build a client library that call 3rd API and you want to make sure all parameters are valid before processing. If you want to cast external data to your internal schema, take a look at Tarams

Installation

Adding contrak to your list of dependencies in mix.exs:

def deps do
  [
    {:contrak, "~> 0.1.1"}
  ]
end

Documentation here https://hexdocs.pm/contrak.

Usage

Contrak helps to validate data with given schema:

  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]]

  %{
    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>

  %{
    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

Validations

Contrak uses 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 for more details