Problem with life cycle hooks

Phoenix Forum Questions / Help
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1

I am a bit stumped…

I am trying to attach a life cycle hook to close flash messages automatically after 5 seconds.

I have this code:

defmodule MailManWeb.FlashLive do
  def on_mount(:default, _params, _session, socket) do
    {:cont,
     socket
     |> Phoenix.LiveView.attach_hook(:flash, :handle_params, &send_close/3)
     |> Phoenix.LiveView.attach_hook(:flash, :handle_info, &info/2)}
  end

  def send_close(_params, _uri, socket) do
    Enum.each(Phoenix.LiveView.Utils.get_flash(socket), fn {key, _msg} ->
      Process.send_after(self(), {:close_flash, key}, 5000)
    end)

    {:cont, socket}
  end

  defp info({:close_flash, key}, socket) do
    {:cont, socket |> Phoenix.LiveView.clear_flash(key)}
  end

  defp info(_, socket), do: {:cont, socket}
end

I initially had the Enum.each in the on_mount, but then it wasn’t executed when using a patch navigation.
Problem is now, it is not working on navigate navigation, I get a no function clause matching error on handle_info, it is as if the hook isn’t set.

I tried moving the attach_hook into the send_close function, but then it explodes on patch because the hook is already set.

What am I missing?

2

I just tried to change the send_close to

  def send_close(_params, _uri, socket) do
    Enum.each(Phoenix.LiveView.Utils.get_flash(socket), fn {key, _msg} ->
      Process.send_after(self(), {:close_flash, key}, 5000)
    end)

    {:cont,
     socket
     |> Phoenix.LiveView.detach_hook(:flash, :handle_info)
     |> Phoenix.LiveView.attach_hook(:flash, :handle_info, &info/2)}
  end

It gives no error, but still the :handle_info is not added.

3

OMG, I found it and once I did it is so logical!

I thought it might have been a bug introduced in rc of live_view, so I created a test app with 0.20.17. I created the hook added 2 pages with just a button that put_flash and push_navigate, immediately I noticed that upon clicking the flash would close after 5 seonds - great - but I also got

[debug] warning: undefined handle_info in TestHookWeb.Page2Live. Unhandled message: {:close_flash, "info"}

This decided me to try and return {:halt, ...} from info/2 and that fixed it!

Returning {:cont, ...} made live_view continue the event where it failed because I have an handle_info/2 but not for that event.