@spec __using__(opts :: []) :: any()

Converts the module into an Ecto.Schema and add factory functions to create structs.

Using

• Ecto.Schema
• Ecto.Type

Derives

• Jason.Encoder

Usage

defmodule MyValueObject do
  use OnePiece.Commanded.ValueObject

  embedded_schema do
    field :title, :string
    # ...
  end
end

Overridable

• validate/2 to add custom validation to the existing changeset/2 without overriding the whole changeset/2 function.

    defmodule MyValueObject do
      use OnePiece.Commanded.ValueObject
  
      embedded_schema do
        field :amount, :integer
      end
  
      def validate(changeset, attrs) do
        changeset
        |> Changeset.validate_number(:amount, greater_than: 0)
      end
    end

• changeset/2 returns an Ecto.Changeset.t/0 for a given value object struct.

  Overriding Changeset

  Be careful when overriding changeset/2 because the default implementation takes care of cast, validate_required the @enforced_keys and nested embeds. You may want to call OnePiece.Commanded.ValueObject.changeset/2 to have such features.

  If you only need to extend the changeset, you can override the validate/2 function instead.

Returns an Ecto.Changeset.t/0 for a given value object struct.

It reads the @enforced_keys from the struct and validates the required fields. Also, it casts the embeds. It is useful when you override the changeset/2 function in your value object.

Examples

defmodule MyValueObject do
  use OnePiece.Commanded.ValueObject

  @enforce_keys [:title, :amount]
  embedded_schema do
    field :title, :string
    field :amount, :integer
  end

  def changeset(message, attrs) do
    message
    |> ValueObject.changeset(attrs)
    |> Changeset.validate_number(:amount, greater_than: 0)
  end
end