djantea

djantea

Building Table Views with Phoenix LiveView: Add a load indicator that will start on user event (click) and end when data finishes loading

Hello @pullrich,

I am following he book, which is great because is helping me building tabelar UI fast. Thank you.

The ideea to separate the individul Phoenix.LiveComponents (sorting, filtering, pagination) from the main LiveView by sending events is great, but it does introduce a UX problem: there is no load indictor that will cover the whole time, starting with the user event (e.g. click on the page number of the pagination form) and ending when the result (the paginated meerkat data) is sent back to the browser.

The current behavior is that the load indicator starts when the user clinks the button and stops when the push event is handled by the handle_event callback. But in the background, the processing of actually fetching the data continues by sending an :update event to the parent LiveView, changing the URI params with push_patch and finally responding to the the URI params change with handle_params. All this subsequent background processing is not covered by the load indicator, and this is normal, as this is a custom way of processing the data. So we need to manually start and stop the progress indicator ourselves.

I tried to solve this problem myself but did not succeed:

I can start the load indicator (the topbar displayed at the top of the page) by replacing:

<div phx-click="show_page"​
     phx-value-page={page_number}​
     phx-target={@myself}​
     class={if current_page?, do: "active"} >

with

<div phx-click={JS.push("show_page") |> JS.dispatch("phx:page-loading-start")}
     phx-value-page={page_number}​
     phx-target={@myself}​
     class={if current_page?, do: "active"} >

But I cannot stop the indicator. I tried by adding this to MeowWeb.MeerkatLive.handle_params/3:

   ...
   |> push_event("phx:page-loading-stop", %{})
   ...

but it does not work. I see the event being sent to the browser through the web socket, but there is no effect, the progress indicator keeps going on.

Any ideas?

Marked As Solved

pullrich

pullrich

Author of Building Table Views with Phoenix LiveView

Hey @djantea ,

thank you for reading my book :slight_smile:

I must admit that it took me a good hour to find the problem here: If you push an event from the server to the client using push_event/3, then you don’t have to prefix the event name with phx: because LiveView does so automatically.

So, in your case, the client would receive the event phx:phx:page-loading-stop which doesn’t stop the loading bar. If you remove the phx: from your push_event/3-call, it should work :slight_smile:

Let me know if this fixed your problem :muscle:

Also Liked

djantea

djantea

Hy @pullrich,

Thank you for taking the time and for responding.

Yes, it solved my problem :slight_smile:

I also realized what the problem was, the next day after I posted the question.

Taking the solution one step further, I decided to use different, custom JavaScript events to be triggered for table loading, phx:table-loading-start and phx:table-loading-stop:

  • After the initial user event is handled by any of the three LiveComponents (clicking on the sort header, on the filter button, or on the page number), right after sending the :update event to the parent LiveView in handle_event/3, I trigger a phx:table-loading-start event:
    ...
    send(self(), {:update, opts})
    {:noreply, push_event(socket, "table-loading-start", %{})}
    ...
  • Then, in the parent LiveView, after the final data is available and is ready to be sent to the browser, in handle_params/3, I trigger a phx:table-loading-stop event:
  def​ handle_params(params, _url, socket) ​do​
    socket =
      socket
      |> parse_params(params)
      |> assign_meerkats()
      |> push_event("table-loading-stop", %{})

      {​:noreply​, socket}
  ​end

And then, I handle these event in JavaScript by starting and stopping the page loading progress indicator, while also preventing the handler of the LiveView’s phx:page-loading-stop event to stop the progress if it has been started by a phx:table-loading-start event:

window.tableLoading = false;

window.addEventListener('phx:table-loading-start', info => {
  window.tableLoading = true
  topbar.show()
})
window.addEventListener('phx:table-loading-stop', info => {
  window.tableLoading = false
  topbar.hide()
})

window.addEventListener("phx:page-loading-start", info => {
  topbar.show()
})
window.addEventListener("phx:page-loading-stop", info => {
  if (!window.tableLoading)
    topbar.hide()
})

I think this is a cleaner solution, because it separates the table loading events, which are spanning across more than one LiveView event → handle_event cycle, from LiveView events which are more fine grained.

But I admit its not the cleanest approach, and I am still looking to improve it.

I feel that more control over the page loading (and maybe other kinds of loading) events should be exposed by LiveView itself, for situations like this.

What do you think?

Where Next?

Popular Pragmatic Bookshelf topics Top

jeffmcompsci
Title: Design and Build Great Web APIs - typo “https://company-atk.herokuapp.com/2258ie4t68jv” (page 19, third bullet in URL list) Typo:...
New
raul
Hi Travis! Thank you for the cool book! :slight_smile: I made a list of issues and thought I could post them chapter by chapter. I’m rev...
New
alanq
This isn’t directly about the book contents so maybe not the right forum…but in some of the code apps (e.g. turbo/06) it sends a TURBO_ST...
New
patoncrispy
I’m new to Rust and am using this book to learn more as well as to feed my interest in game dev. I’ve just finished the flappy dragon exa...
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
dsmith42
Hey there, I’m enjoying this book and have learned a few things alredayd. However, in Chapter 4 I believe we are meant to see the “&gt;...
New
Henrai
Hi, I’m working on the Chapter 8 of the book. After I add add the point_offset, I’m still able to see acne: In the image above, I re...
New
EdBorn
Title: Agile Web Development with Rails 7: (page 70) I am running windows 11 pro with rails 7.0.3 and ruby 3.1.2p20 (2022-04-12 revision...
New
ggerico
I got this error when executing the plot files on macOS Ventura 13.0.1 with Python 3.10.8 and matplotlib 3.6.1: programming_ML/code/03_...
New

Other popular topics Top

Devtalk
Hello Devtalk World! Please let us know a little about who you are and where you’re from :nerd_face:
New
New
PragmaticBookshelf
Andy and Dave wrote this influential, classic book to help their clients create better software and rediscover the joy of coding. Almost ...
New
AstonJ
Continuing the discussion from Thinking about learning Crystal, let’s discuss - I was wondering which languages don’t GC - maybe we can c...
New
Margaret
Hello everyone! This thread is to tell you about what authors from The Pragmatic Bookshelf are writing on Medium.
1147 29994 760
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
PragmaticBookshelf
Author Spotlight Mike Riley @mriley This month, we turn the spotlight on Mike Riley, author of Portable Python Projects. Mike’s book ...
New
PragmaticBookshelf
Programming Ruby is the most complete book on Ruby, covering both the language itself and the standard library as well as commonly used t...
New
New
PragmaticBookshelf
Use advanced functional programming principles, practical Domain-Driven Design techniques, and production-ready Elixir code to build scal...
New

Sub Categories: