A Brief Introduction to Phoenix and LiveView (Part 1)

Hello, once again! Today, I am going to introduce you to the basics of the web framework, Phoenix. Phoenix is a web framework that reached 1.0 in 2015 written in the Elixir programming language. It is generally seen as the “successor” to Ruby on Rails, although that can be hotly debated and is not the purpose of this post. It is well known for its use of the real-time package, LiveView, which can help minimize the amount of Javascript that you have to write. It is well-suited for programmers who want a combination of functionality and performance. If that sounds like you, let’s jump right in!

Installation

I will assume that you have Elixir 1.14 installed. We are going to be using Phoenix version 1.7.0-rc.2 in this tutorial. To install it, run the following command in your terminal:

mix archive.install hex phx_new 1.7.0-rc.2

Creating the App

Great! Now, let’s begin our Phoenix project by using the mix phx.new command:

mix phx.new todo

Great! Now let’s cd into the new todo directory and run the following commands:

cd todo
mix ecto.create

Great! That created the initial PostgreSQL database for us. Now, let’s run the following command to make sure everything was set up correctly:

iex -S mix phx.server

Now browse to localhost:4000 and you should see the Phoenix welcome page. If not, you will need to debug the reason you are getting your specific error.

Creating the Todos

First, let’s take a look at the help dialog that ships with Phoenix by running the following command:

mix help phx.gen.live

Feel free to read this at your convenience. Now, let’s create the Todos using the following command:

mix phx.gen.live Items TodoItem todo_items text:string

Next, follow the instructions printed to your terminal about modifying your router.ex file.

Next, run the generated database migrations:

mix ecto.migrate

Now restart the Phoenix server and re-navigate to localhost:4000/todo_items and you should see the listing page for your TodoItems. Great!

Navigating the Generated Code

Now that we have the Todo app up-and-running, let’s navigate through the code to get a glimpse at how things work under the hood.

lib/todo_web/live/todo_item_live/index.ex

First, let’s take a look at index.ex, the generated Elixir code for the index LiveView. We notice five functions:

mount
handle_params
apply_action
handle_event
list_todo_items

mount is called when the client connects and is used to set up the initial socket. You will notice that there is no render function, and that is because Phoenix uses a particular convention to display its templates: if there is an associated index.html.heex adjacent to index.ex, that template will be used.

handle_params is called whenever we have a live navigation event. These events are what you would normally have separate HTTP requests for. You can learn more about handle_params here:

https://hexdocs.pm/phoenix_live_view/Phoenix.LiveView.html#c:handle_params/3

handle_event is called whenever we have a JS “delete” event pushed to the page. Finally, list_todo_items simply calls the associated context’s function.

Next Up

Join me next time when we dive into index.html.heex. In the mean time, feel free to browse through the additional generated code.

If you gained value from this post, feel free to throw me a dollar or two on my Buy Me a Coffee page, which you can find here:

https://www.buymeacoffee.com/danieljaouen

Your support goes to the cost of keeping the server up and is never unappreciated. Thanks!


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