sodapopcan
To get to the crux of this question right away: Does LiveView always do a first render without any assigns?
So I’m using a struct as one of my assigns. Imagine I’m the url being something like https://mydomain.com/some_id:
defmodule MyAppWeb.HomeLive do
use MyAppWeb, :live_view
@default_assigns [
record: nil, # The default here will never be used, hence `nil`. I tried giving it a default and it doesn't solve my problem.
another_key: "that has a dynamic value but needs a default"
]
def mount(%{"record_id" => record_id}, _session, socket) do
record = Records.find_record(record_id)
{:ok, assign(socket, @default_assigns |> Keyword.replace!(:record, record))}
end
end
Then in my template:
<div><%= @record.some_key %></div>
No matter what, even though my page loads seemingly without a hitch, I always get an error that “nil.some_key is not a function”.
I can, of course, fix this with:
<div<%= @record && @record.some_key %></div>
but I’m confused about the lifecycle here… does the template always render once without been passed any assigns? OR am I just doing something completely wrong?
Thanks!
Where Next?
Trending in Questions
Other Trending Topics
Latest Phoenix Threads
Latest on Elixir Forum
Sponsor Spotlight
Catch errors, track performance, monitor hosts and more.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #deployment
- #library
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #elixirconf
- #channels
- #exunit
- #discussion
- #code-sync
- #podcasts
- #javascript
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ecto-query
- #blog-post
- #elixirconf-us
- #elixir-ls
- #ai
- #phoenix_html
- #iex
- #graphql
- #genstage
- #websockets
- #supervisor
- #advent-of-code
- #distillery
- #processes
- #api
- #forms
- #hex
- #security
- #metaprogramming
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
Catch errors, track performance, monitor hosts and more.
Error tracking, logs, uptime, and Just Enough APM. Built for developers.
Elixir, Erlang & BEAM conferences from Code Sync - join us in 2026!
Practical resources that improve the lives of professional developers.
Master modern tools, write cleaner code, and tackle real-world challenges.
Bringing learning, work and compliance together since 1987.
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"
Showing Posts 1 to 5- Show Best Posts
- Show All (oldest first)
- Show All (newest first)
hectorsq
Hi,
The first param for assign should be a socket.
{:ok, assign(socket, @default_assigns |> Keyword.replace!(:record, record))}ityonemo
It’s been a few months, but IIRC the liveview lifecycle is as such:
However, with the code you have here, it seems like it should always get something out of the find_record.
I’m not sure about your assign function call. unless am I wrong, that you’re supposed to call
assign(socket, key, value)and it will put it in the right place in thesocket.assignfield. I would drop IO.inspects afterRecords.find_record(...)and after theassigns(...)call to check up on what datastructures are being pushed around. If you use VScode this could help:https://slickb.it/bits/70
sodapopcan
Sorry, that was a typo! I’m properly calling
assign(socket, ...)in my actual code.hectorsq
You also defined @defaul_assigns (missing t) and are using @default_assigns
No, the first render uses the data in assigns that is initialized in mount
sodapopcan
Thank you both for your responses. I realize it’s because I’m doing something pretty cavalier that isn’t well represented in my sample code. It’s because my route matches on any root path, so
/:record_id. This of course means that requests forfavicon.icois matching