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

telemachus
Python Testing With Pytest - Chapter 2, warnings for “unregistered custom marks” While running the smoke tests in Chapter 2, I get these...
New
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
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
hgkjshegfskef
The test is as follows: Scenario: Intersecting a scaled sphere with a ray Given r ← ray(point(0, 0, -5), vector(0, 0, 1)) And s ← sphere...
New
hazardco
On page 78 the following code appears: &lt;%= link_to ‘Destroy’, product, class: ‘hover:underline’, method: :delete, data: { confirm...
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
rainforest
Hi, I’ve got a question about the implementation of PubSub when using a Phoenix.Socket.Transport behaviour rather than channels. Before ...
New
andreheijstek
After running /bin/setup, the first error was: The foreman' command exists in these Ruby versions: That was easy to fix: gem install fore...
New
New
dachristenson
I just bought this book to learn about Android development, and I’m already running into a major issue in Ch. 1, p. 20: “Update activity...
New

Other popular topics Top

PragmaticBookshelf
Write Elixir tests that you can be proud of. Dive into Elixir’s test philosophy and gain mastery over the terminology and concepts that u...
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
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
In case anyone else is wondering why Ruby 3 doesn’t show when you do asdf list-all ruby :man_facepalming: do this first: asdf plugin-upd...
New
PragmaticBookshelf
Build efficient applications that exploit the unique benefits of a pure functional language, learning from an engineer who uses Haskell t...
New
AstonJ
Was just curious to see if any were around, found this one: I got 51/100: Not sure if it was meant to buy I am sure at times the b...
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
Leverage Elixir and the Nx ecosystem to build intelligent applications that solve real-world problems in computer vision, natural languag...
New
PragmaticBookshelf
Lint your docs like code: turn any style guide into enforceable rules with Vale and publish clear, consistent content every time. ...
New

Sub Categories: