That would be almost perfect but how does the “abstract” widget get the other assigns if I don’t call it as a function but rather the way you wrote above?
silverdr
LostKobrakai
def queue_widget(assigns) do
pass_through = assigns_to_attributes(assigns, [])
assigns =
assigns
|> assign(:widget_title, gettext("Queue"))
|> assign(:widget_id, "queue")
|> assign(:pass_through, pass_through)
|> assign_new(:inner_block, fn -> [] end)
~H"""
<.widget widget_title={@widget_title} widget_id={@widget_id} {@pass_through}>
<%= if Enum.empty?(@inner_block) do %>
…queue widget default
<% else %>
<%= render_slot(@inner_block) %>
<% end %>
</.widget>
"""
end
1
silverdr
Thank you, Benjamin. While this is noticeably more verbose than what I admittedly was hoping for. It still looks to me more “correct” than what I do now. And… it can probably be shortened to:
<.widget {assigns_to_attributes(assigns, [])}>
without introducing the pass_through part, can’t it? Seems to work and is more pleasing to the eye 
0
LostKobrakai
I’d be cautious about change tracking though – that’s one of the reasons why assigns is not just a dump map you can edit.
1
silverdr
silverdr
Might be Captain Obvious but noticed that doing simply
<.widget {assigns}>
seems to work too. Tried to check this against change tracking docs but am still unsure about the change tracking reliability in such case/usage. Do you have any pointers?
0
mayel
Oh re-checking the docs it doesn’t say, but if other sources I’ve seen like LiveView Assigns: Three Common Pitfalls and Their Solutions | AppSignal Blog are correct then it is a problem for change tracking. Would be good to have a definitive answer (and update the docs if needed…) pinging @chrismccord 
1
mayel
Ah I found another source and the relevant phrase in the docs which confirms it: Assigns and HEEx templates — Phoenix LiveView v1.2.5
Generally speaking, avoid accessing variables inside LiveViews, as code that access variables is always executed on every render. This also applies to the
assignsvariable.
I’d find it useful if LiveView added something like @assigns for cases where you need it, like when using assigns_to_attributes.
1
silverdr
I read that paragraph in the docs too. But I couldn’t be sure whether doing things like <.widget {assigns}> constitutes “accessing variables inside LiveViews” - IOW whether it is equivalent to e. g. <%= assigns.my_assign %> or more to calling widget(assigns) and how do the two differ from change tracking perspective. The second source you linked to, lists the two constructs next to each other though. OTOH I am still not sure how does the approach, which @LostKobrakai suggested (with assigns_to_attributes/2 and @pass_thorugh) sidestep the issue.
0
LostKobrakai
The key is assign(assigns, key, …) if you’re manipulating or adding values/keys. If you’re not doing that it should be fine.
0