An Elixir library that converts keys in maps between snake_case and camel_case.

Useful as a plug in Phoenix for converting incoming params from JavaScript's camelCase to Elixir's snake_case

Converts all keys in maps to snake case ProperCase.to_snake_case/1

Converts all keys in maps to camel case ProperCase.to_camel_case/1

Converts a string to snake case ProperCase.snake_case/1

Converts a string to camel case ProperCase.camel_case/1

# Before:
%{"user" => %{
    "firstName" => "Han",
    "lastName" => "Solo",
    "alliesInCombat" => [
      %{"name" => "Luke", "weaponOfChoice" => "lightsaber"},
      %{"name" => "Chewie", "weaponOfChoice" => "bowcaster"},
      %{"name" => "Leia", "weaponOfChoice" => "blaster"}
    ] 
  }
} 

# After:
%{"user" => %{
    "first_name" => "Han",
    "last_name" => "Solo",
    "allies_in_combat" => [
      %{"name" => "Luke", "weapon_of_choice" => "lightsaber"},
      %{"name" => "Chewie", "weapon_of_choice" => "bowcaster"},
      %{"name" => "Leia", "weapon_of_choice" => "blaster"}
    ]
  }
}

ProperCase is extremely useful as a part of your connection pipeline, converting incoming params from JavaScript's camelCase to Elixir's snake_case

Plug it into your router.ex connection pipeline like so:

  pipeline :api do
    plug :accepts, ["json"]
    plug ProperCase.Plug.SnakeCaseParams
  end

Set phoenix's json encoder in config/config.exs, this way ProperCase will camelCase your data before encoding to JSON:

  :phoenix, :format_encoders, json: ProperCase.JSONEncoder.CamelCase

To ensure that outgoing params are converted to camelCase, define a custom JSON encoder that runs a transform before encoding to json.

def MyApp.CustomJSONEncoder do
  use ProperCase.JSONEncoder, transform: &ProperCase.to_camel_case/1
end

config.exs

  :phoenix, :format_encoders, json: MyApp.CustomJSONEncoder

If available in Hex, the package can be installed as:

1. Add proper_case to your list of dependencies in mix.exs:

   def deps do [{:proper_case, "~> 1.0.2"}] end

2. Ensure proper_case is started before your application:

   def application do [applications: [:proper_case]] end

• Johnny Ji
• Shaun Dern