TIL, 2018-02-24, Ecto and Plugs

Musings

• Time-saver: To save shit in iex>, you still need to alias HabitsOne.Repo, then save things like Repo.insert(changeset).

• Immutability in Javascript: The copying part/massive cloning.
• Erlang shell: erl. Get Erlang versin: erl -eval 'erlang:display(erlang:system_info(otp_release)), halt().' -noshell Reference
• Wow composition of changesets are really cool.
• Then you can separate the validation from the saving.
• Method names for variable: doesn’t exist. Reference
  • String.module_info(:exports).
  • iex> i hello => inspect?
  • iex> exports Ecto.Changeset, readable format.
  • iex> h Ecto.changeset to browse documentation without exiting the terminal.
• IEx History: Reference
• Keyword:
  • A set of functions for working with keywords.

Programming Phoenix, Studying Ecto

• Sample debugging when trying to insert things

def registration_changeset(model, params) do
  aw = model
        # creates an Ecto.Changeset instance from the model, blank changes
        |> changeset(params)
        # cast: applies the given params as changes for the data according to the given set of keys.
        |> cast(params, ~w(password), [])
        # applies a required validator. if no password, still pass through the function but add an error to the changeset
        |> validate_required(:password)
        # applies a length validator
        |> validate_length(:password, min: 6, max: 100)
        # calling another function which can transform the changeset (change attributes, add an error) or not
        |> put_pass_hash()

  require IEx; IEx.pry
  # Because of immutability, you need to have an assignment to the "changed model". You can't just do `model` here because you get the untouched model.
  # This is actually cool because you can then do things step by step as long as you assign and re-assign.
  # At this point, you can call `Repo.insert(aw)`

  aw # Still have to return the changed model or inserted model
end

• Pattern match to get the user_params from the inbound form.
• Create a registration changeset, and if it’s valid, we insert it and present the result to the user.
• If not, render the same thing, with the changeset.
• Controller is separate from change policies in the model layer.
• Model layer has no side effects. (Repo takes care of inserting).
• Changeset = data structure that tracks changes and their validity.

Programming Phoenix, Plugs

• Module plugs: a module that provides 2 functions. plug Plug.Logger.
• Function plugs: single function. plug :protect_from_forgery.