Phoenix released 1.7.0 with Liveview 0.18.16 and introduced Streams for liveview. At first it was not clear to me how to replace my current prepend logic from the published blog So I reached out to its creator of phoenix Chris McCord on twitter and he not only responded, even took out time to review my code and share what would be the way to get it done with stream. This is why elixir community is awesome.
The thing that was not clear from the blog post introducing streams was how would one send additional data over streams that is part of the page but not the actual stream.My apps stream dashboard used prepend and it clearly could benefit from the streams and was an obvious choice for upgrade with streams release.
Here is how the old liveview prepend code
defmodule KyubiWeb.Stream.LiveView do
use KyubiWeb, :live_view
@cache :kyubi_cachex
def mount(_params, _session, socket) do
if connected?(socket), do: KyubiWeb.Endpoint.subscribe("dns")
{:ok, init_stream(socket), temporary_assigns: [cards: []]}
end
def handle_info(%{event: "stream", payload: query}, socket) do
{:noreply,
assign(
socket,
cards: Kyubi.Stream.Card.populate(query, socket.id),
term: get_filter_term(socket.id),
kyubi_node: Kyubi.Utility.Helper.nodename()
)}
end
def handle_event(
_event,
%{"filter" => %{"term" => incoming_query_filter}},
socket
) do
if String.trim(incoming_query_filter) == "",
do: Cachex.del(@cache, socket.id),
else: Cachex.put(@cache, socket.id, {:ok, incoming_query_filter})
{:noreply,
assign(
socket,
cards: Kyubi.Stream.Card.new(),
term: incoming_query_filter
)}
end
def init_stream(socket) do
assign(
socket,
cards: Kyubi.Stream.Card.new(),
term: get_filter_term(socket.id),
kyubi_node: Kyubi.Utility.Helper.nodename()
)
end
def get_filter_term(socket_id) do
case Cachex.get(@cache, socket_id) do
{:ok, {:ok, filter}} ->
filter
{:ok, nil} ->
""
end
end
end
<div class="row mb-3 mx-3">
<div id="dns-stream" phx-update="prepend" class="mb-3 mx-3 col">
<%= for query <- @cards.queries do %>
<p id={query.resource_event_id} />
<div
id={"dns-query-#{query.resource_status}%>-#{query.resource_event_id}"}
class={"card text-white bg-dark
border border-#{@cards.label.message_type} mb-3 mr-3 ml-3"}
>
<KyubiWeb.Components.Stream.card
query={query}
label={@cards.label}
favicon={@cards.favicon}
ad_tracker={@cards.ad_tracker}
/>
<p class="card-text">
<small class="text-muted">
<%= query.client_user_agent %> <%= query.client_ip %>,
<%= query.client_city %>
</small>, <img
src={~p"/kyubi/images/flags/#{@cards.country_flag_code}"}
height="14"
/>
</p>
</div>
<% end %>
</div>
</div>
Here is the updated liveview code based on streams
defmodule KyubiWeb.Stream.LiveView do
use KyubiWeb, :live_view
@cache :kyubi_cachex
def mount(_params, _session, socket) do
if connected?(socket), do: KyubiWeb.Endpoint.subscribe("dns")
{:ok, init_stream(socket)}
end
def handle_info(%{event: "stream", payload: query}, socket) do
{:noreply,
assign(
socket,
term: get_filter_term(socket.id),
kyubi_node: Kyubi.Utility.Helper.nodename()
)
|> stream_insert(:cards, Kyubi.Stream.Card.populate(query, socket.id), at: 0)}
end
def handle_event(
_event,
%{"filter" => %{"term" => incoming_query_filter}},
socket
) do
if String.trim(incoming_query_filter) == "",
do: Cachex.del(@cache, socket.id),
else: Cachex.put(@cache, socket.id, {:ok, incoming_query_filter})
{:noreply,
assign(
socket,
term: incoming_query_filter
)
|> stream_insert(:cards, Kyubi.Stream.Card.new(), at: 0)}
end
def init_stream(socket) do
assign(
socket,
term: get_filter_term(socket.id),
kyubi_node: Kyubi.Utility.Helper.nodename()
)
|> stream(:cards, [Kyubi.Stream.Card.new()])
end
def get_filter_term(socket_id) do
case Cachex.get(@cache, socket_id) do
{:ok, {:ok, filter}} ->
filter
{:ok, nil} ->
""
end
end
end
<div class="row mb-3 mx-3">
<div id="dns-stream" phx-update="prepend" class="mb-3 mx-3 col">
<%= for query <- @cards.queries do %>
<p id={query.resource_event_id} />
<div
id={"dns-query-#{query.resource_status}%>-#{query.resource_event_id}"}
class={"card text-white bg-dark
border border-#{@cards.label.message_type} mb-3 mr-3 ml-3"}
>
<KyubiWeb.Components.Stream.card
query={query}
label={@cards.label}
favicon={@cards.favicon}
ad_tracker={@cards.ad_tracker}
/>
<p class="card-text">
<small class="text-muted">
<%= query.client_user_agent %> <%= query.client_ip %>,
<%= query.client_city %>
</small>, <img
src={~p"/kyubi/images/flags/#{@cards.country_flag_code}"}
height="14"
/>
</p>
</div>
<% end %>
</div>
</div>
Streams definitely have a better developer experience compared to the append and prepend design. At times the release docs or blog posts don't cover all the use cases that are out there implemented and stalls upgrades. The elixir community makes it possible for the developers to adopt the latest changes seamlessly
Top comments (2)
Shouldn't you update your template to be
<div id="dns-stream" phx-update="stream"instead of<div id="dns-stream" phx-update="prepend"?Hi @darnahsan , this is a great new feature in our Elixir/Phoenix community. In my side project I also replaced temporary assigns with streams and sure it's working fine as espected. One thing I miss is ability to clear/reset whole stream and insert more items at once. For example I have a form on the same page with list(that form filters list according to some criteria). When I need to reset the list, for now I only can collect doom id's from items(using the phx-hook), assign them to the socket and delete all items from stream(for loop) by using stream_delete_by_dom_id/3.