ecto_sandbox

mix.exs

defmodule EctoSandbox.Mixfile do
  use Mix.Project

  def project do
    [app: :ecto_sandbox,
     version: "0.1.0",
     elixir: "~> 1.4",
     build_embedded: Mix.env == :prod,
     start_permanent: Mix.env == :prod,
     elixirc_paths: ["."],
     deps: deps()]
  end

  def application do
    [extra_applications: [:logger]]
  end

  defp deps do
    [{:ecto, "~> 2.1"}]
  end
end

user.ex

defmodule User do
  use Ecto.Schema

  schema "users" do
    field :name, :string
    field :age, :integer, default: 0
  end
end

weather.ex

defmodule Weather do
  use Ecto.Schema

  schema "weather" do
    field :city
    field :temp_lo, :integer
    field :temp_hi, :integer
    field :prcp,    :float, default: 0.0 # 降水量
  end

  def changeset(weather, params \\ %{}) do
    weather
    |> Ecto.Changeset.change(params)
    |> Ecto.Changeset.validate_required([:city, :temp_lo, :temp_hi])
    |> Ecto.Changeset.validate_number(:prcp, greater_than_or_equal_to: 0.0)
  end
end