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

abtin
page 20: … protoc command… I had to additionally run the following go get commands in order to be able to compile protobuf code using go...
New
jon
Some minor things in the paper edition that says “3 2020” on the title page verso, not mentioned in the book’s errata online: p. 186 But...
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
AleksandrKudashkin
On the page xv there is an instruction to run bin/setup from the main folder. I downloaded the source code today (12/03/21) and can’t see...
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
brunogirin
When I run the coverage example to report on missing lines, I get: pytest --cov=cards --report=term-missing ch7 ERROR: usage: pytest [op...
New
brunogirin
When installing Cards as an editable package, I get the following error: ERROR: File “setup.py” not found. Directory cannot be installe...
New
brunogirin
When trying to run tox in parallel as explained on page 151, I got the following error: tox: error: argument -p/–parallel: expected one...
New
dachristenson
@mfazio23 Android Studio will not accept anything I do when trying to use the Transformations class, as described on pp. 140-141. Googl...
New
roadbike
From page 13: On Python 3.7, you can install the libraries with pip by running these commands inside a Python venv using Visual Studio ...
New

Other popular topics Top

PragmaticBookshelf
Andy and Dave wrote this influential, classic book to help their clients create better software and rediscover the joy of coding. Almost ...
New
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
AstonJ
Or looking forward to? :nerd_face:
503 15149 280
New
Exadra37
Please tell us what is your preferred monitor setup for programming(not gaming) and why you have chosen it. Does your monitor have eye p...
New
PragmaticBookshelf
From finance to artificial intelligence, genetic algorithms are a powerful tool with a wide array of applications. But you don't need an ...
New
PragmaticBookshelf
Build efficient applications that exploit the unique benefits of a pure functional language, learning from an engineer who uses Haskell t...
New
PragmaticBookshelf
Author Spotlight Rebecca Skinner @RebeccaSkinner Welcome to our latest author spotlight, where we sit down with Rebecca Skinner, auth...
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
AstonJ
Curious what kind of results others are getting, I think actually prefer the 7B model to the 32B model, not only is it faster but the qua...
New

Sub Categories: