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# Action Cable -- Integrated websockets for Rails # Action Cable – Integrated websockets for Rails
Action Cable seamlessly integrates websockets with the rest of your Rails application. Action Cable seamlessly integrates websockets with the rest of your Rails application.
It allows for real-time features to be written in Ruby in the same style It allows for real-time features to be written in Ruby in the same style
@ -36,29 +36,31 @@ reflections of each unit.
## A full-stack example ## A full-stack example
The first thing you must do is defined your ApplicationCable::Connection class in Ruby. This The first thing you must do is defined your `ApplicationCable::Connection` class in Ruby. This
is the place where you do authorization of the incoming connection, and proceed to establish it is the place where you do authorization of the incoming connection, and proceed to establish it
if all is well. Here's the simplest example starting with the server-side connection class: if all is well. Here's the simplest example starting with the server-side connection class:
# app/channels/application_cable/connection.rb ```ruby
module ApplicationCable # app/channels/application_cable/connection.rb
class Connection < ActionCable::Connection::Base module ApplicationCable
identified_by :current_user class Connection < ActionCable::Connection::Base
identified_by :current_user
def connect
self.current_user = find_verified_user def connect
end self.current_user = find_verified_user
protected
def find_verified_user
if current_user = User.find cookies.signed[:user_id]
current_user
else
reject_unauthorized_connection
end
end
end end
protected
def find_verified_user
if current_user = User.find cookies.signed[:user_id]
current_user
else
reject_unauthorized_connection
end
end
end end
end
```
This relies on the fact that you will already have handled authentication of the user, and This relies on the fact that you will already have handled authentication of the user, and
that a successful authentication sets a signed cookie with the user_id. This cookie is then that a successful authentication sets a signed cookie with the user_id. This cookie is then
@ -69,9 +71,11 @@ potentially disconnect them all if the user is deleted or deauthorized).
The client-side needs to setup a consumer instance of this connection. That's done like so: The client-side needs to setup a consumer instance of this connection. That's done like so:
# app/assets/javascripts/cable.coffee ```coffeescript
@App = {} # app/assets/javascripts/cable.coffee
App.cable = Cable.createConsumer "http://cable.example.com" @App = {}
App.cable = Cable.createConsumer "http://cable.example.com"
```
The http://cable.example.com address must point to your set of Action Cable servers, and it The http://cable.example.com address must point to your set of Action Cable servers, and it
must share a cookie namespace with the rest of the application (which may live under http://example.com). must share a cookie namespace with the rest of the application (which may live under http://example.com).
@ -89,59 +93,63 @@ Here's a simple example of a channel that tracks whether a user is online or not
First you declare the server-side channel: First you declare the server-side channel:
# app/channels/appearance_channel.rb ```ruby
class AppearanceChannel < ApplicationCable::Channel # app/channels/appearance_channel.rb
def subscribed class AppearanceChannel < ApplicationCable::Channel
current_user.appear def subscribed
end current_user.appear
def unsubscribed
current_user.disappear
end
def appear(data)
current_user.appear on: data['appearing_on']
end
def away
current_user.away
end
end end
The #subscribed callback is invoked when, as we'll show below, a client-side subscription is initiated. In this case, def unsubscribed
current_user.disappear
end
def appear(data)
current_user.appear on: data['appearing_on']
end
def away
current_user.away
end
end
```
The `#subscribed` callback is invoked when, as we'll show below, a client-side subscription is initiated. In this case,
we take that opportunity to say "the current user has indeed appeared". That appear/disappear API could be backed by we take that opportunity to say "the current user has indeed appeared". That appear/disappear API could be backed by
Redis or a database or whatever else. Here's what the client-side of that looks like: Redis or a database or whatever else. Here's what the client-side of that looks like:
# app/assets/javascripts/cable/subscriptions/appearance.coffee ```coffeescript
App.appearance = App.cable.subscriptions.create "AppearanceChannel", # app/assets/javascripts/cable/subscriptions/appearance.coffee
connected: -> App.appearance = App.cable.subscriptions.create "AppearanceChannel",
# Called once the subscription has been successfully completed connected: ->
# Called once the subscription has been successfully completed
appear: ->
@perform 'appear', appearing_on: @appearingOn()
away: ->
@perform 'away'
appearingOn: ->
$('main').data 'appearing-on'
$(document).on 'page:change', -> appear: ->
App.appearance.appear() @perform 'appear', appearing_on: @appearingOn()
$(document).on 'click', '[data-behavior~=appear_away]', -> away: ->
App.appearance.away() @perform 'away'
false
Simply calling App.cable.subscriptions.create will setup the subscription, which will call AppearanceChannel#subscribed, appearingOn: ->
which in turn is linked to original App.consumer -> ApplicationCable::Connection instances. $('main').data 'appearing-on'
We then link App.appearance#appear to AppearanceChannel#appear(data). This is possible because the server-side $(document).on 'page:change', ->
App.appearance.appear()
$(document).on 'click', '[data-behavior~=appear_away]', ->
App.appearance.away()
false
```
Simply calling `App.cable.subscriptions.create` will setup the subscription, which will call `AppearanceChannel#subscribed`,
which in turn is linked to original `App.consumer` -> `ApplicationCable::Connection` instances.
We then link `App.appearance#appear` to `AppearanceChannel#appear(data)`. This is possible because the server-side
channel instance will automatically expose the public methods declared on the class (minus the callbacks), so that these channel instance will automatically expose the public methods declared on the class (minus the callbacks), so that these
can be reached as remote procedure calls via App.appearance#perform. can be reached as remote procedure calls via `App.appearance#perform`.
Finally, we expose App.appearance to the machinations of the application itself by hooking the #appear call into the Finally, we expose `App.appearance` to the machinations of the application itself by hooking the `#appear` call into the
Turbolinks page:change callback and allowing the user to click a data-behavior link that triggers the #away call. Turbolinks `page:change` callback and allowing the user to click a data-behavior link that triggers the `#away` call.
## Channel example 2: Receiving new web notifications ## Channel example 2: Receiving new web notifications
@ -153,26 +161,29 @@ action on the client.
This is a web notification channel that allows you to trigger client-side web notifications when you broadcast to the right This is a web notification channel that allows you to trigger client-side web notifications when you broadcast to the right
streams: streams:
# app/channels/web_notifications.rb ```ruby
class WebNotificationsChannel < ApplicationCable::Channel # app/channels/web_notifications.rb
def subscribed class WebNotificationsChannel < ApplicationCable::Channel
stream_from "web_notifications_#{current_user.id}" def subscribed
end stream_from "web_notifications_#{current_user.id}"
end end
end
```
```coffeescript
# Somewhere in your app this is called, perhaps from a NewCommentJob
ActionCable.server.broadcast \
"web_notifications_1", { title: 'New things!', body: 'All shit fit for print' }
# Somewhere in your app this is called, perhaps from a NewCommentJob # Client-side which assumes you've already requested the right to send web notifications
ActionCable.server.broadcast \ App.cable.subscriptions.create "WebNotificationsChannel",
"web_notifications_1", { title: 'New things!', body: 'All shit fit for print' } received: (data) ->
web_notification = new Notification data['title'], body: data['body']
```
# Client-side which assumes you've already requested the right to send web notifications The `ActionCable.server.broadcast` call places a message in the Redis' pubsub queue under the broadcasting name of "web_notifications_1".
App.cable.subscriptions.create "WebNotificationsChannel",
received: (data) ->
web_notification = new Notification data['title'], body: data['body']
The ActionCable.server.broadcast call places a message in the Redis' pubsub queue under the broadcasting name of "web_notifications_1".
The channel has been instructed to stream everything that arrives at "web_notifications_1" directly to the client by invoking the The channel has been instructed to stream everything that arrives at "web_notifications_1" directly to the client by invoking the
#received(data) callback. The data is the hash sent as the second parameter to the server-side broadcast call, JSON encoded for the trip `#received(data)` callback. The data is the hash sent as the second parameter to the server-side broadcast call, JSON encoded for the trip
across the wire, and unpacked for the data argument arriving to #received. across the wire, and unpacked for the data argument arriving to `#received`.
## Dependencies ## Dependencies