Understanding Phoenix LiveView
- Setup (this article)
- The Primitives
- Building a Gallery app
Subscribe to get FREE Tutorials by email. Start learning Elixir and Phoenix to build features and apps!
Phoenix LiveView has been released on Hex! Although it's still not a stable release (at the time of writing 0.3.1), it works really well and it's packed of cool features.
Since the first version, I'm so impressed with how easy and fast I can develop a real-time application with LiveView, without using a complex JavaScript framework.
But to me, the most important LiveView's aspect is the productivity boost! Be able to focus on where data reside and are processed while being sure that changes are pushed to the front-end, updating the UI automatically. It really feels like magic!
In this article we see how to get started with Phoenix LiveView by creating a new Phoenix app and going through the LiveView setup.
In the next articles we’ll see how to use this setup to build a super-simple LiveView application called Gallery, which we’ll use to develop our first LiveView page and understand how LiveView works under the hood.
In this app the user can interact with the LiveView page and go through a gallery of images by clicking the interface buttons.
Create a new Phoenix project
Let's first create a new Phoenix project. We need the latest stable Phoenix Framework and Node.js installed.
$ mix phx.new gallery --no-ecto
Since we don't need any database, we use the --no-ecto
option. Our gallery will just be a list of image urls.
Now, how can we setup LiveView?
At the moment there are no LiveView generators, so we need to manually integrate it, changing some files and macros.
:phoenix_live_view
in mix.exs
Let's start by adding the phoenix_live_view library under the mix.exs
dependencies. We can set the release version we find on Hex
defp deps do
[
{:phoenix, "~> 1.4.10"},
...
{:phoenix_live_view, "~> 0.3.1"}
]
end
or if you prefer to try the latest committed code, you can directly use the GitHub LiveView master branch
defp deps do
[
{:phoenix, "~> 1.4.10"},
...
{:phoenix_live_view, github: "phoenixframework/phoenix_live_view"}
]
end
In our case we set the 0.3.1 version and get the dependencies running mix deps.get
in the terminal
$ mix deps.get
...
New:
phoenix_live_view 0.3.1
* Getting phoenix_live_view (Hex package)
Signing salt in config/config.exs
Now we need to update the endpoint configuration in config/config.exs
, adding the LiveView signing salt.
To generate a new salt we use the mix task
$ mix phx.gen.secret 32
LIlgBfJ9j7xLJ6Almy982/ZydK/9y0vd
# config/config.exs
config :gallery, GalleryWeb.Endpoint,
...
live_view: [
signing_salt: "LIlgBfJ9j7xLJ6Almy982/ZydK/9y0vd"
]
LiveView Flash plug
Then, we add the LiveView Flash plug to our :browser
pipeline in lib/gallery_web/router.ex
, just after :fetch_flash
# lib/gallery_web/router.ex
pipeline :browser do
...
plug :fetch_flash
plug Phoenix.LiveView.Flash
...
end
Imports in lib/gallery_web.ex
We now update the lib/gallery_web.ex
web file, adding some import
s to the controller
, view
and router
functions
# lib/gallery_web.ex
def controller do
quote do
...
import Phoenix.LiveView.Controller
end
end
def view do
quote do
...
import Phoenix.LiveView,
only: [live_render: 2, live_render: 3, live_link: 1, live_link: 2]
end
end
def router do
quote do
...
import Phoenix.LiveView.Router
end
end
Socket in lib/gallery_web/endpoint.ex
Next, we expose a new socket for LiveView updates in the endpoint module lib/gallery_web/endpoint.ex
. This socket is used by LiveView to send updates and receive events.
defmodule GalleryWeb.Endpoint do
use Phoenix.Endpoint, otp_app: :gallery
socket "/live", Phoenix.LiveView.Socket
...
end
JavaScript and CSS
Now let's focus on the client side - we need to add the LiveView JavaScript library in assets/package.json
.
{
"dependencies": {
...
"phoenix_live_view": "file:../deps/phoenix_live_view"
}
}
This library will run on the browser, updating the DOM, managing user events while talking with the LiveView process on the server.
To install the new javascript dependency we've just added, run
$ npm install --prefix assets
We are almost ready, we just need to add four lines of javascript code in assets/js/app.js
, which starts LiveView on the client
// assets/js/app.js
import {Socket} from "phoenix"
import LiveSocket from "phoenix_live_view"
let liveSocket = new LiveSocket("/live", Socket)
liveSocket.connect()
and import the default LiveView CSS in assets/css/app.css
/* assets/css/app.css */
@import "../../deps/phoenix_live_view/assets/css/live_view.css";
Done! Let's see if everything works
Great, the setup is finished and LiveView is ready! Let's see now if everything works by creating a super-simple LiveView module that renders some text.
After creating the lib/gallery_web/live
directory, we open in it a new file called gallery_live.ex
. In this new file we define the GalleryWeb.GalleryLive
module (our LiveView page - just copy/paste the code below, we will dig into LiveView functionalities in next articles)
defmodule GalleryWeb.GalleryLive do
use Phoenix.LiveView
def mount(_session, socket) do
{:ok, socket}
end
def render(assigns) do
~L"""
<h1>LiveView is awesome!</h1>
"""
end
end
Inside the render/1
function we have a LiveView template that will show on our browser the message LiveView is awesome!.
Almost there... we just need to add a live
route in our router lib/gallery_web/router.ex
# lib/gallery_web/router.ex
defmodule GalleryWeb.Router do
use GalleryWeb, :router
...
scope "/", GalleryWeb do
...
live "/gallery", GalleryLive
end
end
and after running the Phoenix server
$ mix phx.server
[info] Running GalleryWeb.Endpoint with cowboy 2.7.0 at 0.0.0.0:4000 (http)
[info] Access GalleryWeb.Endpoint at http://localhost:4000
...
opening the page http://localhost:4000/gallery we should see our LiveView page.
What's next
In the following article, the Primitives of Phoenix LiveView we learn the LiveView basics, exploring the Phoenix LiveView primitives, understanding the magic behind LiveView while learning how we can build a simple counter.
Take also a look at the Phoenix LiveView documentation. It's a great read which gives a solid understanding of how things work and which kind of features are available.
Another great resource is the chrismccord/phoenix_live_view_example GitHub repo, where you find easy code examples showing all the different LiveView's features.
Subscribe to get FREE Tutorials by email. Start learning Elixir and Phoenix to build features and apps!
Top comments (0)