Hello Experts,
I am just starting to play with Supervisors and I have created the Project using mix new podder --sup
I get the Following error when I try to Invoke a Process using the Dynamic Supervisor.
This is my code.

I am using Elixir 1.7.3.

Applicaiton.ex

defmodule Podder.Application do
  # See https://hexdocs.pm/elixir/Application.html
  # for more information on OTP Applications
  @moduledoc false
  use Application

  def start(_type, _args) do
    # List all child processes to be supervised
    children = [
      # Starts a worker by calling: Podder.Worker.start_link(arg)
      # {Podder.Worker, arg},
      %{
        id: Podder.DynamicSupervisor,
        start: {Podder.DynamicSupervisor, :start_link, []}
      }
    ]

    # See https://hexdocs.pm/elixir/Supervisor.html
    # for other strategies and supported options
    opts = [strategy: :one_for_one, name: Podder.DynamicSupervisor]
    Supervisor.start_link(children, opts)
  end
end

Supervisor

defmodule Podder.DynamicSupervisor do
  use DynamicSupervisor

  def start_link() do
DynamicSupervisor.start_link(__MODULE__, :ok, name: __MODULE__)
  end

  @doc """
  Server Side
  """
  def init(_arg) do
DynamicSupervisor.init(strategy: :one_for_one)
  end

  def start_work do
{:ok, pid} = start_podcast_server
  end

  defp start_podcast_server do
spec = %{id: Podder, start: {Podder, :start_link, []}}
DynamicSupervisor.start_child(__MODULE__, spec)
  end
end

GenServer

defmodule Podder do
  use GenServer

  @moduledoc """
  Documentation for Podder.
  """

  @doc """
  Hello world.

  ## Examples

      iex> Podder.hello()
      :world

  """
  def init(state) do
    {:ok, state}
  end

  def handle_call(:fetch, _from, state) do
    new_state = Map.put(state, "fetched", 1)
    {:reply, new_state, new_state}
  end

  def handle_call(:get_state, _from, state) do
    {:reply, state, state}
  end

  @doc """
  Client Implementation
  """
  def start_link(state) do
    GenServer.start_link(__MODULE__, state)
  end

  def fetch_episodes(pid) do
    GenServer.call(pid, :fetch)
  end

  def get_episodes(pid) do
    GenServer.call(pid, :get_state)
  end
end

I am trying this from iex

iex(4)> Podder.DynamicSupervisor.start_work
** (MatchError) no match of right hand side value: {:error, {:invalid_child_spec, {{Podder, :start_link, []}, :permanent, 5000, :worker, [Podder]}}}
    (podder) lib/podcastsupervisor.ex:16: Podder.DynamicSupervisor.start_work/0
iex(4)>