confirmation_schema.ex

defmodule Sched.Confirmation.Schema do
  use SchedWeb.Web, :model

  @primary_key {:id, :binary_id, autogenerate: true}
  schema "confirmations" do
    field :message, :string
    field :number, :string
    field :awaiting_reply, :boolean, default: true
    field :flagged, :boolean, default: false
    field :reply, :string

    belongs_to :appointment, Sched.Appointment.Schema, type: :binary_id
    belongs_to :client, Sched.Client.Schema, type: :binary_id

    timestamps
  end


  @required_on_creation ~w(
    appointment_id
    client_id
    message
    number
  )

  @optional_on_update ~w(
    reply
    flagged
    message
    number
    awaiting_reply
  )

  def create(params) do
    %__MODULE__{}
    |> cast(params, @required_on_creation, ~w())
    |> unique_constraint(:number, name: :index_confirmations_on_receiving)
  end

  def update(model, params) do
    model
    |> cast(params, ~w(), @optional_on_update)
  end

  def confirm(model) do
    model
    |> change(flagged: false, awaiting_reply: false)
    # |> cast_assoc(:appointment, with: &Sched.Appointment.Schema.confirm/2, required: true)
    # TODO: Ecto 2.0
  end
end

repo.ex

try do
  # Worst case scenario: We will never send a text message to a client before committing to our database of the request.
  # This will prevent two text messages ever from going out for the same event
  confirmation = ConfirmationSchema.create(%{appointment_id: appointment_id, client_id: client_id, message: body, number: number}) |> @repo.insert!()
  {:ok, message} = Sched.SMS.send(to: number, body: body)
  confirmation = ConfirmationSchema.update(confirmation, %{message: message.body, number: message.to}) |> @repo.update!()
  {:ok, message.status}
rescue
  err in [Ecto.InvalidChangesetError] ->
  IO.inspect err
  # Repo is no longer accessible now.
  {:error, :already_sent}
end

err gives:

%Ecto.InvalidChangesetError{action: :insert,
 changeset: %Ecto.Changeset{action: :insert,
  changes: %{appointment_id: "a76b5f6c-1124-4abf-b926-74fbb265fa19",
    awaiting_reply: true, client_id: "f56e7c8b-97ff-4adb-aac4-29603a58ad6f",
    flagged: false, id: nil, inserted_at: nil, message: "Don't forget!",
    number: "+18055555555", reply: nil, updated_at: nil},
  constraints: [%{constraint: "index_confirmations_on_receiving",
     field: :number, message: "has already been taken", type: :unique}],
  errors: [number: "has already been taken"], filters: %{},
  model: %Sched.Confirmation.Schema{__meta__: #Ecto.Schema.Metadata<:built>,
   appointment: #Ecto.Association.NotLoaded<association :appointment is not loaded>,
   appointment_id: nil, awaiting_reply: true,
   client: #Ecto.Association.NotLoaded<association :client is not loaded>,
   client_id: nil, flagged: false, id: nil, inserted_at: nil, message: nil,
   number: nil, reply: nil, updated_at: nil}, optional: [], opts: [],
  params: %{"appointment_id" => "a76b5f6c-1124-4abf-b926-74fbb265fa19",
    "client_id" => "f56e7c8b-97ff-4adb-aac4-29603a58ad6f",
    "message" => "Don't forget!", "number" => "+18055555555"}, prepare: [],
  repo: SchedWeb.Repo,
  required: [:appointment_id, :client_id, :message, :number],
  types: %{appointment_id: :binary_id, awaiting_reply: :boolean,
    client_id: :binary_id, flagged: :boolean, id: :binary_id,
    inserted_at: Ecto.DateTime, message: :string, number: :string,
    reply: :string, updated_at: Ecto.DateTime}, valid?: false, validations: []}}