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
sdmoralesma
Title: Web Development with Clojure, Third Edition - migrations/create not working: p159 When I execute the command: user=&gt; (create-...
New
mikecargal
Title: Hands-On Rust (Chap 8 (Adding a Heads Up Display) It looks like ​.with_simple_console_no_bg​(SCREEN_WIDTH*2, SCREEN_HEIGHT*2...
New
herminiotorres
Hi @Margaret , On page VII the book tells us the example and snippets will be all using Elixir version 1.11 But on page 3 almost the en...
New
raul
Page 28: It implements io.ReaderAt on the store type. Sorry if it’s a dumb question but was the io.ReaderAt supposed to be io.ReadAt? ...
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
jskubick
I found an issue in Chapter 7 regarding android:backgroundTint vs app:backgroundTint. How to replicate: load chapter-7 from zipfile i...
New
digitalbias
Title: Build a Weather Station with Elixir and Nerves: Problem connecting to Postgres with Grafana on (page 64) If you follow the defau...
New
brunogirin
When running tox for the first time, I got the following error: ERROR: InterpreterNotFound: python3.10 I realised that I was running ...
New
tkhobbes
After some hassle, I was able to finally run bin/setup, now I have started the rails server but I get this error message right when I vis...
New

Other popular topics Top

wolf4earth
@AstonJ prompted me to open this topic after I mentioned in the lockdown thread how I started to do a lot more for my fitness. https://f...
New
siddhant3030
I’m thinking of buying a monitor that I can rotate to use as a vertical monitor? Also, I want to know if someone is using it for program...
New
Exadra37
I am asking for any distro that only has the bare-bones to be able to get a shell in the server and then just install the packages as we ...
New
mafinar
Crystal recently reached version 1. I had been following it for awhile but never got to really learn it. Most languages I picked up out o...
New
rustkas
Intensively researching Erlang books and additional resources on it, I have found that the topic of using Regular Expressions is either c...
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
Rails 7 completely redefines what it means to produce fantastic user experiences and provides a way to achieve all the benefits of single...
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
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: