Elixir DateTime

event.ex

defmodule Repro.Event do
  use Repro.Web, :model

  schema "events" do
    field :title, :string
    field :location, :string
    field :date, Ecto.Date
    field :description, :string

    timestamps()
  end

  @doc """
  Builds a changeset based on the `struct` and `params`.
  """
  def changeset(struct, params \\ %{}) do
    struct
    |> cast(params, [:title, :location, :date, :description])
    |> validate_required([:title, :location, :date, :description])
    |> validate_change(:date, &must_be_future/2)
  end


  defp must_be_future(_, value) do
    Ecto.DateTime.compare(Ecto.DateTime.from_date(value), Ecto.DateTime.utc)
    |> get_error
  end

  defp get_error(comparison) when comparison == :lt do
    [date: "cant be in the past"]
  end

  defp get_error(_), do: []
end