cro

cro

Programming Phoenix LiveView: P27, live_path confusion

I am working on the “Your Turn” for chapter one and building out the restart button talked about on page 27. It recommends looking into the live_patch function to patch the view and add the button. Many examples involving live_patch I found on the web suggested something like

<%= live_patch to: Routes.live_path(@socket, __MODULE__), replace: true do %>
   <button>Try again!</button>
<%end>

but Elixir complains with

warning: Routes.live_path/2 is undefined (module Routes is not available or is yet to be defined)
  lib/pento_web/live/wrong_live.ex:50: PentoWeb.WrongLive.render/1

mix phx.routes says the helper is defined:

$ mix phx.routes
          page_path  GET  /                                      Phoenix.LiveView.Plug :index
          live_path  GET  /guess                                 Phoenix.LiveView.Plug PentoWeb.WrongLive
live_dashboard_path  GET  /dashboard                             Phoenix.LiveView.Plug :home
live_dashboard_path  GET  /dashboard/:page                       Phoenix.LiveView.Plug :page
live_dashboard_path  GET  /dashboard/:node/:page                 Phoenix.LiveView.Plug :page
          websocket  WS   /live/websocket                        Phoenix.LiveView.Socket
           longpoll  GET  /live/longpoll                         Phoenix.LiveView.Socket
           longpoll  POST  /live/longpoll                         Phoenix.LiveView.Socket
          websocket  WS   /socket/websocket                      PentoWeb.UserSocket

So I must be missing a use or alias somewhere? Help?

Marked As Solved

SophieDeBenedetto

SophieDeBenedetto

Author of Programming Phoenix LiveView

Hello and thank you all for your patience! A lot has changed in LiveView lately and Bruce and I are hard at work on a new version of the book with the latest version and all new code samples. Keep an eye out for that in the next few weeks.

In the meantime, yes the live path helpers have been replaced with the link/1 function component Phoenix.Component — Phoenix LiveView v0.19.5.

I believe the latest version of the book that is currently out does reflect this change though. Please do make sure you’re working off of the latest version. If you’ve purchased the e-book, you’ll be emailed when a new Beta release is made available for download and you’ll have access to download it for free.

Also Liked

SophieDeBenedetto

SophieDeBenedetto

Author of Programming Phoenix LiveView

Re-posting here for visibility bc I accidentally replied privately:

Mystery solved!

At the top of your PentoWeb.WrongLive module, you should pull in the LiveView behavior like this:

defmodule PentoWeb.WrongLive do
  use PentoWeb, :live_view

I think there was someplace in the book where we gave you an outdated instruction to do so like this instead:

defmodule PentoWeb.WrongLive do
  use Phoenix.LiveView

That has since been corrected but I’m not sure if the fix is out in the Beta release from last week or if it will be included in the next one. In either case, that is the change you need to make and I’m sorry for any confusion this caused!

Let me know if this un-sticks you or if you encounter any other errors :slight_smile:
And @cro confirmed this fixed the issue!

SophieDeBenedetto

SophieDeBenedetto

Author of Programming Phoenix LiveView

Hi @IwateKyle, I’m sorry to hear that you found this particular exercise so challenging. Rest assured that live_patch is covered in greater detailed later on in the book and we will update the text to let readers know.

In the meantime, here is some guidance on the solution:

  • Per the docs here (and as shown in the original question on this thread above), you can write the live_patch function call in the markup in the render function of WrongLive like this:
<%= live_patch to: Routes.live_path(@socket, __MODULE__), replace: true do %>
      <button>Try again!</button>
<%end%>

This adds a button that is wrapped in a special kind of link called a “live patch”. A “live patch” link basically re-directs to the current live view without reloading it. From the docs, if you call live_patch with the route to the current live view…

…the new state is pushed to the client, without reloading the whole page while also maintaining the current scroll position

The value of the :to key in the argument to live_patch can be any route. To specify the route of the current live view, you use: Routes.live_path(@socket, __MODULE__) or you could use Routes.live_path(@socket, PentoWeb.WrongLive), which evaluates to the same thing. The third example in the docs here is accurate https://hexdocs.pm/phoenix_live_view/Phoenix.LiveView.Helpers.html#live_patch/2-examples.

To fully get this working, you need to add this live_patch link I described above, and you need to implement a new function in your live view, a handle_params/3 function. From the docs:

When navigating to the current LiveView, Phoenix.LiveView.handle_params/3 is immediately invoked to handle the change of params and URL state.

If you follow the link to the handle_params/3 docs, you will see that it takes in three arguments: some params, the URI and the socket, and it needs to return {:noreply, socket}. If we are aiming to “reset” the game, then we should return a socket with the appropriate starting state. So something like this:

def handle_params(_params, _uri, socket) do
    {
      :noreply,
      assign(
        socket,
        score: 0,
        message: "Guess a number."
      )
    }
  end

That should do it! I hope this helps and thanks very much for your feedback.

IwateKyle

IwateKyle

Bless you Sophie. You are a super star! I appreciate your time. I’ve since moved ahead, but I’ll definitely add this to exercise. :slight_smile:

Where Next?

Popular Pragmatic Bookshelf topics Top

jesse050717
Title: Web Development with Clojure, Third Edition, pg 116 Hi - I just started chapter 5 and I am stuck on page 116 while trying to star...
New
yulkin
your book suggests to use Image.toByteData() to convert image to bytes, however I get the following error: "the getter ‘toByteData’ isn’t...
New
jamis
The following is cross-posted from the original Ray Tracer Challenge forum, from a post by garfieldnate. I’m cross-posting it so that the...
New
gilesdotcodes
In case this helps anyone, I’ve had issues setting up the rails source code. Here were the solutions: In Gemfile, change gem 'rails' t...
New
leba0495
Hello! Thanks for the great book. I was attempting the Trie (chap 17) exercises and for number 4 the solution provided for the autocorre...
New
AndyDavis3416
@noelrappin Running the webpack dev server, I receive the following warning: ERROR in tsconfig.json TS18003: No inputs were found in c...
New
fynn
This is as much a suggestion as a question, as a note for others. Locally the SGP30 wasn’t available, so I ordered a SGP40. On page 53, ...
New
akraut
The markup used to display the uploaded image results in a Phoenix.LiveView.HTMLTokenizer.ParseError error. lib/pento_web/live/product_l...
New
AufHe
I’m a newbie to Rails 7 and have hit an issue with the bin/Dev script mentioned on pages 112-113. Iteration A1 - Seeing the list of prod...
New
dtonhofer
@parrt In the context of Chapter 4.3, the grammar Java.g4, meant to parse Java 6 compilation units, no longer passes ANTLR (currently 4....
New

Other popular topics Top

New
PragmaticBookshelf
Use WebRTC to build web applications that stream media and data in real time directly from one user to another, all in the browser. ...
New
mafinar
This is going to be a long an frequently posted thread. While talking to a friend of mine who has taken data structure and algorithm cou...
New
AstonJ
We’ve talked about his book briefly here but it is quickly becoming obsolete - so he’s decided to create a series of 7 podcasts, the firs...
New
PragmaticBookshelf
Author Spotlight Jamis Buck @jamis This month, we have the pleasure of spotlighting author Jamis Buck, who has written Mazes for Prog...
New
PragmaticBookshelf
Author Spotlight: VM Brasseur @vmbrasseur We have a treat for you today! We turn the spotlight onto Open Source as we sit down with V...
New
First poster: bot
zig/http.zig at 7cf2cbb33ef34c1d211135f56d30fe23b6cacd42 · ziglang/zig. General-purpose programming language and toolchain for maintaini...
New
First poster: AstonJ
Jan | Rethink the Computer. Jan turns your computer into an AI machine by running LLMs locally on your computer. It’s a privacy-focus, l...
New
sir.laksmana_wenk
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc. However, I don’t...
New
AstonJ
This is a very quick guide, you just need to: Download LM Studio: https://lmstudio.ai/ Click on search Type DeepSeek, then select the o...
New

Sub Categories: