chapter-14.md

Chapter.14 What's Next

Other Interesting Features

Supporting Internationalization with Gettext

• Gettext is there for i18n internationalization & l10n localization support

• can auto-extract translations from code

VideologueWeb.Gettext gets generated on Phoenix project creation; used in error_helper.ex

• different language translations are in priv/gettext dir; with pre-set Ecto file errors.pot & translations in priv/gettext/en/LC_MESSAGES

Intercepting on Phoenix Channels

• a broadcast message, Phoenix sends to PubSub system sent to all sockets (this is fastlaning since bypasses channels)

• Phoenix Channels provide intercept feature allowing channels to intercept broadcast message

• for each intercept-ed event, a handle_out clause shall be defined to handle event

• Phoenix would send message to all sockets, each channel processing intercepted message

• useful while evolving code, with performance price

Understanding Phoenix Live Reload

• used to propagate live changes; with a channel receiving filesystem events & a plug injecting live-reload iframe on every request

Phoenix PubSub Adapter

• uses Erlang by default ensuring broadcast works across multiple nodes, requires all machines to be connected as per Erlang Distribution Protocol

• supports multiple adapters like Redis Adapter

Phoenix Clients for Other Platforms

• Phoenix Channels are using WebSockets, working with ES6 & other platforms

• Channels are Transport Agnostic; can use Custom Protocol to support special requirement

Phoenix LiveView

is a lib for building rich interactive bi-directional apps without writing custom JS; example

• represent a webpage as a function over web state

• establishes messages and callbacks to change state

• allows browser events such as MouseClick, FormSubmit, KeyPress to send events

Handling Links in a Counter

• in router.ex

import Phoenix.LiveView.Router
##
live "/counter", CounterLive

• add lib/some_web/live/counter.ex

defmodule SomeWeb.CounterLive do
  use Phoenix.LiveView

  def render(assigns) do
    ~L"""
    <div>
      <h1>count: <%= @val %></h1>
      <button phx-click="boom" class="alert-danger">BOOM</button>
      <button phx-click="dec">-</button>
      <button phx-click="inc">+</button>
    </div>
    """
  end

  def mount(_session, socket), do: {:ok, assign(socket, :val, 0)}

  def handle_event("inc", _, socket), do: {:noreply, :val, &(&1 + 1)}

  def handle_event("dec", _, socket), do: {:noreply, :val, &(&1 - 1)}
end

Validating Forms

• with core functions like following, assuming form for new user

...
  def render(assigns) do
    Phoenix.View.render(SomeWeb.UserView, "new.html", assigns)
  end

  def mount(_session, socket) do
    {
      :ok,
      assign(socket, changeset: Accounts.change_user(%User{}))
    }
  end

  def handle_event("save", %{"user" => user_params}, socket) do
    Accounts.create_user(user_params) |> do_save()
  end
  defp do_save({:ok, user}) do
    {:stop, socket
            |> put_flash(:info, "user created")
            |> redirect(to: Routes.live_path(socket, UserLive.show, user))}
  end
  defp do_save({:error, %Ecto.changeset{} = changeset}) do
    {:noreply, assign(socket, changeset: changeset)}
  end
...

Phoenix PubSub 2.0

• custom adapters could be provided to use

• PubSub doesn't start as part of Endpoint anymore, need to explicitly provide in Supervision Tree

Phoenix and Telemetry Integration

• provides Telemetry Developers a unified API for metrics dispatch & instrumentation

• provides a way collecting built-in VM metrics

• gives a unified theme for consuming & reporting metrics

• Telemetry, a dynamic dispatching lib for metrics & instrumentation

• Telemetry Poller, allows periodically collection of measurements and dispatch of events

• Telemetry Metrics, provides common interface defining metrics

• Telemetry Registry, for event declaration, discovery & registration

talk: ElixirConf 2020

Good Luck!

Keep Practicing

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