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

New
ianwillie
Hello Brian, I have some problems with running the code in your book. I like the style of the book very much and I have learnt a lot as...
New
simonpeter
When I try the command to create a pair of migration files I get an error. user=&gt; (create-migration "guestbook") Execution error (Ill...
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
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
curtosis
Running mix deps.get in the sensor_hub directory fails with the following error: ** (Mix) No SSH public keys found in ~/.ssh. An ssh aut...
New
adamwoolhether
Is there any place where we can discuss the solutions to some of the exercises? I can figure most of them out, but am having trouble with...
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
kolossal
Hi, I need some help, I’m new to rust and was learning through your book. but I got stuck at the last stage of distribution. Whenever I t...
New
redconfetti
Docker-Machine became part of the Docker Toolbox, which was deprecated in 2020, long after Docker Desktop supported Docker Engine nativel...
New

Other popular topics Top

ohm
Which, if any, games do you play? On what platform? I just bought (and completed) Minecraft Dungeons for my Nintendo Switch. Other than ...
New
Exadra37
I am thinking in building or buy a desktop computer for programing, both professionally and on my free time, and my choice of OS is Linux...
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
AstonJ
Curious to know which languages and frameworks you’re all thinking about learning next :upside_down_face: Perhaps if there’s enough peop...
New
AstonJ
There’s a whole world of custom keycaps out there that I didn’t know existed! Check out all of our Keycaps threads here: https://forum....
New
PragmaticBookshelf
Tailwind CSS is an exciting new CSS framework that allows you to design your site by composing simple utility classes to create complex e...
New
DevotionGeo
The V Programming Language Simple language for building maintainable programs V is already mentioned couple of times in the forum, but I...
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
New
PragmaticBookshelf
Author Spotlight: Peter Ullrich @PJUllrich Data is at the core of every business, but it is useless if nobody can access and analyze ...
New

Sub Categories: