crud_macro.ex

defmodule Operations do 
  @moduledoc """
  Examples: 
    
    operations Schema.Trip, :trip
    operations Schema.User, :user, only: [:get, :delete]
    # supports :plural option for list_x function
    operations Schema.Datum, :datum, plural: :data
  """
  defmacro operations(schema, name) do
    quote do 
      operations(unquote(schema), unquote(name), [])
    end
  end

  defmacro operations(schema, name, opts) do
    quote location: :keep do 
      ops = Keyword.get(unquote(opts), :only, [:list, :get, :delete])

      if :list in ops do 
        def unquote(:"list_#{Keyword.get(opts, :plural, :"#{name}s")}")() do 
          Repo.all(unquote(schema))
        end
      end

      if :get in ops do 
        def unquote(:"get_#{name}")(id) do 
          Repo.get(unquote(schema), id)
        end
        def unquote(:"get_#{name}!")(id) do 
          Repo.get!(unquote(schema), id)
        end
      end

      if :delete in ops do 
        def unquote(:"delete_#{name}")(id) do 
          unquote(schema)
          |> Repo.get!(unquote(schema), id)
          |> Repo.delete
        end
        def unquote(:"delete_#{name}!")(id) do 
          unquote(schema)
          |> Repo.get!(unquote(schema), id)
          |> Repo.delete!
        end
      end
    end
  end
end