TIL, 2018-02-20, Programming Phoenix, Day 2

Musings

• Phoenix sample app: Reference
• Layers in Rails: Reference
  • Internal API for the app, but surrounded by: HTTP interface, Database access, Logger, File storage, Messaging.
  • If simple app, then you can speed things up by integrating the HTTP code with the actual app.
  • When you have additional interfaces (user actions, cron jobs, bash scripts), you need something inside.
  • Bigger app: HTTP, CLI, events/jobs, database access, logger, file storage, messaging.
  • Comparison: ActionController, Rake, Resque, Sequel, Rails.logger, Fog/S3, ActionMailer.
  • Possible entrance to the app:

class ApplicationController < ActionController::Base
  attr_reader :app
  helper_method :app

  before_filter :setup_app

  private

  def setup_app
    @app = MyShinyApp.new(session[:user_id])
  end
end

• Phoenix is doing this via Contexts. Reference
• h String or h Enum.map in IEx to learn things about Elixir!
• alias HabitsOne.User to not need to constantly have HabitsOne.User, just use User. Reference
• Linux: cd - to toggle between directories.

Programming Phoenix

• alias User: Bring in HabitsOne.User to iex.
• IEx.Helpers.recompile to reload the current Mix application. Reference
  • This worked, I also tried r HabitsOne.User but it didn’t recompile.
• Enumerable: find to get the first match only, filter to get all matches. Also Elixir’s Enumerable is bigger than Ruby’s!
• First model:

defmodule HabitsOne.Repo do
  @moduledoc """
  In memory repository.
  """

  def all(HabitsOne.User) do
    [
      %HabitsOne.User{id: "1", name: "Daryll", username: "daryllxd", password: "daryllxd"},
      %HabitsOne.User{id: "2", name: "Jerico", username: "jerico", password: "jerico"},
      %HabitsOne.User{id: "3", name: "Justin", username: "justin", password: "justin"}
    ]
  end

  def all(_module), do: []

  # Given a module, iterate over and get all records with the same ID
  def get(module, id) do
    Enum.find all(module), fn map -> map.id == id end
  end

  #
  def get_by(module, params) do
    Enum.find all(module), fn map ->
      Enum.all?(params, fn {key, val} -> Map.get(map, key) == val end)
    end
  end
end

iex> alias HabitsOne.User
iex> alias HabitOne.Repo

iex> Repo.all User
iex> Repo.get(User, "1")
iex> Repo.get_by User, name: "Jerico", password: "jerico"

• Different error for no UserController, not having user HabitsOne.Web, :controller, and not having the right index action.
• Error: cannot expand Struct User: You did not alias HabitsOne.User.
• Debugging:

require IEx; IEx.pry
$ iex -S mix phoenix.server

pry> respawn # Kills the iex process and spins a new one up at the same place in the code

• Migrations: $ mix ecto.gen.migration create_user
• Insert: Repo.insert(%HabitsOne.User{ name: name, email: "#{name}@yahoo.com", password_hash: "hehe" })
• Link to path: <%= link "All Users", to: user_path(@conn, :index) %>
• $ mix phx.routes: $ rake routes
• Chapter 3: There’s an error in def changeset(model, params \ :empty), you need to change :empty to :invalid Reference
• So smart: Changesets