# String-based Enum

To define a string-based Enumeration, you can just use a keyword of strings
as the enumerator-list.

**NOTE**: For a string-based Enumeration, every enumerator must have an
initializer.

For more details about macros generated by `SimpleEnum.defenum/2`, feels free
to check it's documentation.

## Example

    # lib/my_app/person.ex
    defmodule MyApp.Person do
      import SimpleEnum, only: [defenum: 2]
    
      # Define String-based Enumeration
      defenum :gender, man: "M", woman: "W", unspecified: "U"
    
      defstruct [:gender, :first_name, :last_name]
    
      @type t :: %__MODULE__{
             # We want only keys in our structs...
             gender: gender_keys(),
             first_name: String.t(),
             last_name: String.t()
           }
    
      def cast(%{gender: gender_value, first_name: first_name, last_name: last_name}) do
        %__MODULE__{
          # ... so let's lookup only the key
          gender: gender(gender_value, :key),
          first_name: first_name,
          last_name: last_name
        }
      end
    end

    iex> MyApp.Person.cast(%{gender: :man, first_name: "John", last_name: "Doe"})
    %MyApp.Person{first_name: "John", gender: :man, last_name: "Doe"}
    
    iex> MyApp.Person.cast(%{gender: "M", first_name: "John", last_name: "Doe"})
    %MyApp.Person{first_name: "John", gender: :man, last_name: "Doe"}

    iex> MyApp.Person.cast(%{gender: "W", first_name: "Jane", last_name: "Doe"})
    %MyApp.Person{first_name: "Jane", gender: :woman, last_name: "Doe"}
    
    iex> MyApp.Person.cast(%{gender: "U", first_name: "", last_name: ""})
    %MyApp.Person{first_name: "", gender: :unspecified, last_name: ""}

    iex> MyApp.Person.cast(%{gender: "?", first_name: "", last_name: ""})
    ** (ArgumentError) invalid value "?" for Enum MyApp.Person.gender/2. Expected one of [:man, :woman, :unspecified, "M", "W", "U"]