Croma.Struct

Utility module to define structs and some helper functions.

Using this module requires to prepare modules that represent each struct field. Each of per-field module must provide the following members:

• required: @type t
• required: @spec validate(term) :: Croma.Result.t(t)
• optional: @spec default :: t

Some helpers for defining such per-field modules are available.

• Wrappers of built-in types such as Croma.String, Croma.Integer, etc.
• Utility modules such as Croma.SubtypeOfString to define “subtypes” of existing types.
• Ad-hoc module generators defined in Croma.TypeGen.

To define a struct, use this module with a keyword list:

defmodule S do
  use Croma.Struct, field1_name: Field1Module, field2_name: Field2Module
end

Then the above code is converted to defstruct along with @type t.

This module also generates the following functions.

• @spec new(Dict.t) :: Croma.Result.t(t)
• @spec new!(Dict.t) :: t
• @spec validate(term) :: Croma.Result.t(t)
• @spec validate!(term) :: t
• @spec update(t, Dict.t) :: Croma.Result.t(t)
• @spec update!(t, Dict.t) :: t

Examples

iex> defmodule I do
...>   @type t :: integer
...>   def validate(i) when is_integer(i), do: {:ok, i}
...>   def validate(_), do: {:error, {:invalid_value, [__MODULE__]}}
...>   def default, do: 0
...> end

...> defmodule S do
...>   use Croma.Struct, i: I
...> end

...> S.validate([i: 5])
...> {:ok, %S{i: 5}}

...> S.validate(%{i: "not_an_integer"})
...> {:error, {:invalid_value, [S, I]}}

...> {:ok, s} = S.new([])
...> {:ok, %S{i: 0}}

...> S.update(s, [i: 2])
...> {:ok, %S{i: 2}}

...> S.update(s, %{"i" => "not_an_integer"})
...> {:error, {:invalid_value, [S, I]}}