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!
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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