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I am almost completely new to Rails, or I am sure I would know how to answer this question myself. I am just trying to modify the basic chat app created in the basic ActionCable demo: https://medium.com/@dhh/rails-5-action-cable-demo-8bba4ccfc55e#.6lmd6tfi7
Instead of having just one chat room, I want to have multiple chat rooms, so I modified my routes.rb by adding this line:
get '/rooms/show/:topic', to: 'rooms#show'
So now I can visit different chat rooms based on different topics. The rooms controller at /app/controllers/rooms_controller.rb handles these routes with no problem:
class RoomsController < ApplicationController
def show
@topic = params[:topic]
@messages = Message.all
end
end
But this parameter is not being passed to app/channels/room_channel.rb, and I'm just not sure what modifications I need to make. My current attempt:
class RoomChannel < ApplicationCable::Channel
def subscribed
stream_from "room_channel_#{params[:topic]}"
end
only returns "room_channel_"
580
The problem here was that I failed to understand from where the subscribed method was being called, and thus did not know how to pass parameters to it.
By reading the actioncable documentation: https://github.com/rails/rails/tree/master/actioncable
I found out that the subscribed method is called via client-side javascript, not by the rails controller. In the case of the example chat app, this means I had to change the first line of the file /app/assets/javascripts/channels/room.coffee
App.room = App.cable.subscriptions.create "RoomChannel",
to
App.room = App.cable.subscriptions.create { channel: "RoomChannel", topic: topic},
Passing a javascript object to this method allowed me to access those parameters in the subscribed method of rooms_controller.rb.
97
Set the topic_id in a HTML tag, maybe in the body tag in your layout file.
<body data-topic-id="<%= @topic.id %>">
Now read it from JS like this:
document.querySelector('body').dataset.topicId
Your subscription creation line would look like this:
App.room = App.cable.subscriptions.create (channel: 'RoomChannel', topic_id: document.querySelector('body').dataset.topicId)
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