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

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
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
cro
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 ...
New
jeremyhuiskamp
Title: Web Development with Clojure, Third Edition, vB17.0 (p9) The create table guestbook syntax suggested doesn’t seem to be accepted ...
New
Chrichton
Dear Sophie. I tried to do the “Authorization” exercise and have two questions: When trying to plug in an email-service, I found the ...
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
New
bjnord
Hello @herbert ! Trying to get the very first “Hello, Bracket Terminal!" example to run (p. 53). I develop on an Amazon EC2 instance runn...
New
redconfetti
Docker-Machine became part of the Docker Toolbox, which was deprecated in 2020, long after Docker Desktop supported Docker Engine nativel...
New
New

Other popular topics Top

PragmaticBookshelf
Stop developing web apps with yesterday’s tools. Today, developers are increasingly adopting Clojure as a web-development platform. See f...
New
New
brentjanderson
Bought the Moonlander mechanical keyboard. Cherry Brown MX switches. Arms and wrists have been hurting enough that it’s time I did someth...
New
AstonJ
Just done a fresh install of macOS Big Sur and on installing Erlang I am getting: asdf install erlang 23.1.2 Configure failed. checking ...
New
PragmaticBookshelf
Learn different ways of writing concurrent code in Elixir and increase your application's performance, without sacrificing scalability or...
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 Mike Riley @mriley This month, we turn the spotlight on Mike Riley, author of Portable Python Projects. Mike’s book ...
New
PragmaticBookshelf
Build modern server-driven web applications using htmx. Whatever programming language you use, you’ll write less (and cleaner) code. ...
New
CommunityNews
A Brief Review of the Minisforum V3 AMD Tablet. Update: I have created an awesome-minisforum-v3 GitHub repository to list information fo...
New
RobertRichards
Hair Salon Games for Girls Fun Girls Hair Saloon game is mainly developed for kids. This game allows users to select virtual avatars to ...
New

Sub Categories: