DispatchEx

Compile time dispatch for patterns.

Similar to Elixirs Protocol but uses pattern matching on the value.

Installation

If available in Hex, the package can be installed by adding dispatchex to your list of dependencies in mix.exs:

def project do
  [
    # ...
    compilers: Mix.compilers() ++ [:dispatch]
  ]

def deps do
  [
    # ...
    {:dispatchex, "~> 0.1.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/dispatchex.

Live Reload & Phoenix

To add support for live reload compilation add to reloadable_compilers in config/dev.exs.

config :phxapp_web, PhxApp.Endpoint,
  reloadable_compilers: [:gettext, :phoenix, :elixir, :dispatch],

Simple Usage

defmodule Castable do
  use DispatchEx, :protocol

  @callback cast(term()) :: {:ok, term()} | {:error, atom()}

  # Add optional fallback clause,
  def cast(_), do: {:error, :fallback}
end

defmodule WrappedNumber do
  use DispatchEx, for: Castable

  def cast(%{"type" => "number", "value" => v}), do: {:ok, {:integer, v}}
end

defmodule WrappedString do
  use DispatchEx, for: Castable

  def cast(%{"type" => "string", "value" => v}), do: {:ok, {:string, v}}
end

{:ok, {:string, "abc"}} = Castable.cast(%{"type" => "string", "value" => "abc"})
{:ok, {:integer, 123}} = Castable.cast(%{"type" => "number", "value" => 123})
{:error, :fallback} = Castable.cast(%{})