Tarams

Phoenix request params validation library.

• Why Tarams
• Installation
• Usage
• Define schema
  • Default value
  • Custom cast function
  • Nested schema
• Validation
• Contributors

Why Tarams

- Reduce code boilerplate 
- Shorter schema definition
- Default function which generate value each casting time
- Custom validation functions
- Custom parse functions

Installation

Available in Hex, the package can be installed by adding tarams to your list of dependencies in mix.exs:

def deps do
  [
    {:tarams, "~> 1.0.0"}
  ]
end

Usage

@index_params_schema  %{
    keyword: :string,
    status: [type: :string, required: true],
    group_id: [type: :integer, numer: [greater_than: 0]]
  }

def index(conn, params) do
    with {:ok, better_params} <- Tarams.cast(params, @index_params_schema) do
        # do anything with your params
    else
        {:error, errors} -> # return params error
    end
end

Define schema

Schema is just a map and it can be nested. Each field is defined as

<field_name>: [<field_spec>, ...]

Or short form

<field_name>: <type>

Field specs is a keyword list thay may include:

• type is required, Tarams support same data type as Ecto. I borrowed code from Ecto
• default: default value or default function
• cast_func: custom cast function
• number, format, length, in, not_in, func, required are available validations

Default value

You can define a default value for a field if it's missing from the params.

schema = %{
    status: [type: :string, default: "pending"]
}

Or you can define a default value as a function. This function is evaluated when Tarams.cast gets invoked.

schema = %{
    date: [type: :utc_datetime, default: &Timex.now/0]
}

Custom cast function

You can define your own casting function, tarams provide cast_func option. Your cast_func must follows this spec

fn(any) :: {:ok, any} | {:error, binary} | :error

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

schema = %{
    user_id: [type: {:array, :integer}, cast_func: &my_array_parser/1]
}

Tarams.cast(%{user_id: "1,2,3"}, schema)

This is a demo parser function.

Nested schema

With Tarams you can parse and validate nested map and list easily

@my_schema %{
    status: :string,
    pagination: %{
        page: [type: :integer, number: [min: 1]],
        size: [type: :integer, number: [min: 10, max: 100"]]
    }
}

Or nested list schema

@user_schema %{
    name: :string,
    email: [type: :string, required: true]
    addresses: [type: {:array, %{
        street: :string,
        district: :string,
        city: :string
    }}]
}

Validation

Tarams uses Valdi validation library. You can read more about Valdi here 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

  product_schema = %{
    sku: [type: :string, required: true, length: [min: 6, max: 20]]
    name: [type: :string, required: true],
    quantity: [type: :integer, number: [min: 0]],
    type: [type: :string, in: ~w(physical digital)],
    expiration_date: [type: :naive_datetime, func: &my_validation_func/1]
  }
  

Contributors

If you find a bug or want to improve something, please send a pull request. Thank you!