Coercion

Coerce dirty values to clean Elixir primitive types, with validation.

import Coercion

{:ok, 20} = coerce(" 20 ", :integer)
{:invalid, 0} = coerce("  x", :integer)

{:ok, true} = coerce(" TRue ", :boolean)
{:ok, true} = coerce(" T ", :boolean)
{:ok, true} = coerce(" Y ", :boolean)
{:ok, true} = coerce(" Yes ", :boolean)
{:ok, true} = coerce(" 1 ", :boolean)
{:invalid, false} = coerce(" TRu ", :boolean)
{:ok, false} = coerce(" F ", :boolean)
{:ok, false} = coerce(" N ", :boolean)
{:ok, false} = coerce(" 0 ", :boolean)

{:ok, "hello"} = coerce(" hello ", :string)
{:blank, ""} = coerce("  ", :string)
{:ok, "true"} = coerce(true, :string)
{:ok, "10.5"} = coerce(10.5, :string)

{:ok, %{"one" => "one"}} == coerce(%{"one" => "one"}, :map)
{:invalid, %{}} == coerce("nope", :map)
{:ok, ["one", "two"]} == coerce(["one", "two"], :list)
{:invalid, []} == coerce("nope", :list)

{:ok, ~D[2020-04-02]} = coerce("2020-04-02", :date)
{:ok, ~U[2020-04-02 12:00:01Z]} = coerce("2020-04-02T12:00:01Z", :utc_datetime)
{:ok, ~N[2020-04-02 12:00:01]} = coerce("2020-04-02T12:00:01Z", :naive_datetime)

The primary use case is decoding values that come from external sources where everything is just a String.

Example sources:

• URL-encoded values

  name=Kate&age=40&subscribed=Y
  

• CSV

  name,age,subscribed
  Kate,40,T
  

• XML

  <row>
    <name>Kate</name>
    <age>40</age>
    <subscribed>Yes</subscribed>
  </row>

Ecto.Schema is often a good fit for this type of problem, but sometimes it's overkill.

Installation

The package can be installed by adding coercion to your list of dependencies in mix.exs:

def deps do
  [{:coercion, "~> 1.2"}]
end

Then, run mix deps.get, and you're ready to go.

API Documentation: https://hexdocs.pm/coercion.

License: https://github.com/moxley/coercion/blob/master/LICENSE