Hello everyone,
I am a beginner to elixir and phoenix. I was trying to make a webpage where users can create different discussion topics and in those discussions people can add comments. For commenting I think channels would be great but I am confused that when a user creates a new discussion thread, how will a subtopic be generated for that particular discussion topic in the backend? Initially I can hard code it but is there a way that a topic is generated for channels as soon as a user adds a discussion topic?
Channels are just names. In the Docs you will see that example:
channel "room:*", HelloWeb.RoomChannel
Then there is a join function:
defmodule HelloWeb.RoomChannel do
use Phoenix.Channel
def join("room:lobby", _message, socket) do
{:ok, socket}
end
def join("room:" <> _private_room_id, _params, _socket) do
{:error, %{reason: "unauthorized"}}
end
end
(in this example the private rooms are always refused since the docs talks about implementing the authorization later on).
As long as your join function accepts _private_room_id
as a room name (i.e. it returns ok), then your channel exists, basically.
Thanks I tried it and it worked.
Hello Lud,
Can you give more information on whats on in the foolowing function :
def join("room:" <> _private_room_id, _params, _socket) do
{:error, %{reason: "unauthorized"}}
end
AS i understand, “room:” <> _private_room_id is concatenation, how elixir transform a concatenation in param ?
Hello and welcome,
In that case, it’s a pattern match… and _private_room_id will be assigned to what follow “room:”
To complete @kokolegorille 's response, it means that if your channel is set to “room:*” in your socket module, private_room_id
will be bound to whatever you javascript client sends for this *
.
It can also be simplified like this… maybe it’s more explicit.
iex> "koko:" <> id = "koko:12345"
"koko:12345"
iex> id
"12345"
Woow, ok, thanks for your explanations @kokolegorille and @lud ! this pattern matching feature is sooo great !!