kminevskiy
Hey folks,
Does anyone know what could cause the following behavior: I have a live view template and in it I conditionally render a form (based on the value inside the socket assigns).
<%= if length(@users) > 0 do %>
...
<% end %>
When the length changes, it used to render a form, but now nothing happens. If I prepend that first line with, say, a tag <p><%= length(@users) %></p> Everything (showing the form dynamically based on the length of @users list) works as expected. I am pretty sure the code worked as is a few weeks ago before I updated to the latest Live View (but I’m not even sure it’s an issue with Live View), among other packages. Am I missing some new behavior introduced recently or is there something else I’m not doing correctly?
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PJUllrich
This might not help in this particular case, but I recently learned that a template gets rendered and send over the websocket connection every time the socket assigns are changed when it isn’t in the .leex format, so when it is a .eex file. Just changing all file formats to .leex reduced the websocket traffic by a lot! So, whenever you do
<%= render "my_template.html", assigns %>inside a template, make sure thatmy_templateis of the format .leexkminevskiy
Interesting. Do you know / remember if that was the behavior specific to a certain (earlier) release of LiveView? As I mentioned above, I haven’t had any issues with 0.10.0, but after upgrading to 0.11 (and then to 0.12.x) I encountered the aforementioned issue.
carterbryden
I had a similar issue with conditional rendering with liveview. I posted an issue but I just haven’t had enough time to create a reproduction repo publically (client project). In my case it seemed like it might be related to a nested liveview inside a conditional in a liveview template. Still don’t have a fix for it, I just changed the way I was rendering things to work around needing the if statement. I’ll post here if I do figure it out.
kminevskiy
A quick update: it doesn’t look like I can reproduce this bug (?) on a new installation. I suppose it’s specific to my project and I’ll have to debug on my own. I’ll post the solution in this thread.
kminevskiy
Will be happy to. Let me extract that portion and I’ll create an issue. Thank you!
axelson
Hmm, in that case it seems like it would be worthwhile to provide a reproduction project and post an issue to the project.
kminevskiy
Unfortunately, that didn’t help.
If I add
<p><%= Enum.any?(@users) %></p>above the conditional, everything works as expected (firstfalseis being rendered and then, once an event happens, it switches totrueand the form inside the conditional is rendered).So far, I’ve checked the following:
renderfunction receives pre-computed value (it’s not calculating it on the fly).IO.inspect/1actually renders the list correctly.Let me know if there’s anything else I could try.
axelson
It looks like 0.12.1 isn’t actually released on hex yet. But please report back when you try a version with the fix!
kminevskiy
I was looking at that fix a few minutes ago. I’ll update to 0.12.1 and report back.
axelson
Maybe you could try the master branch. I encountered a fairly similar problem with content disappearing that Chris McCord has fixed on the master branch. I think it is this changelog entry: “Fix component innerHTML being discarded when a sibling DOM element appears above it, in cases where the component lacks a DOM id”