uninitialized constant > ActionCable::Server::Configuration::ApplicationCable

Question

When I am running server its throwing error shown in logs below. I googled a lot but didn't get reason behind it. Somebody please put some light on it.

Gemfile

source 'https://rubygems.org'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '>= 5.0.0.beta1', '< 5.1'
# Use sqlite3 as the database for Active Record
gem 'sqlite3'

gem 'active_model_serializers', '~> 0.10.0.rc1'

group :development, :test do
  gem 'byebug'
end
gem 'puma'
group :development do
  gem 'spring'
end

Logs:

/home/pd/.rvm/gems/ruby-2.2.4/gems/actioncable-5.0.0.beta1/lib/action_cable/server/configuration.rb:15:in
`initialize': uninitialized constant
ActionCable::Server::Configuration::ApplicationCable (NameError)    from
/home/pd/.rvm/gems/ruby-2.2.4/gems/actioncable-5.0.0.beta1/lib/action_cable/server/base.rb:16:in `new'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/actioncable-5.0.0.beta1/lib/action_cable/server/base.rb:16:in `block in <class:Base>'    from
/home/pd/.rvm/gems/ruby-2.2.4/gems/activesupport-5.0.0.beta1/lib/active_support/core_ext/module/attribute_accessors.rb:72:in
`block in mattr_reader'     from
/home/pd/.rvm/gems/ruby-2.2.4/gems/activesupport-5.0.0.beta1/lib/active_support/core_ext/module/attribute_accessors.rb:55:in
`each'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/activesupport-5.0.0.beta1/lib/active_support/core_ext/module/attribute_accessors.rb:55:in
`mattr_reader'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/activesupport-5.0.0.beta1/lib/active_support/core_ext/module/attribute_accessors.rb:208:in
`mattr_accessor'    from
/home/pd/.rvm/gems/ruby-2.2.4/gems/actioncable-5.0.0.beta1/lib/action_cable/server/base.rb:16:in `<class:Base>'     from
/home/pd/.rvm/gems/ruby-2.2.4/gems/actioncable-5.0.0.beta1/lib/action_cable/server/base.rb:12:in `<module:Server>'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/actioncable-5.0.0.beta1/lib/action_cable/server/base.rb:7:in
`<module:ActionCable>'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/actioncable-5.0.0.beta1/lib/action_cable/server/base.rb:6:in
`<top (required)>'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/actioncable-5.0.0.beta1/lib/action_cable.rb:43:in
`server'    from
/home/pd/.rvm/gems/ruby-2.2.4/gems/actioncable-5.0.0.beta1/lib/action_cable/process/logging.rb:10:in
`<top (required)>'  from /home/pd/Documents/EventsApp/config.ru:7:in
`block in <main>'   from
/home/pd/.rvm/gems/ruby-2.2.4/gems/rack-2.0.0.alpha/lib/rack/builder.rb:55:in
`instance_eval'     from
/home/pd/.rvm/gems/ruby-2.2.4/gems/rack-2.0.0.alpha/lib/rack/builder.rb:55:in
`initialize'    from /home/pd/Documents/EventsApp/config.ru:in `new'
    from /home/pd/Documents/EventsApp/config.ru:in `<main>'     from
/home/pd/.rvm/gems/ruby-2.2.4/gems/rack-2.0.0.alpha/lib/rack/builder.rb:49:in
`eval'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/rack-2.0.0.alpha/lib/rack/builder.rb:49:in
`new_from_string'   from
/home/pd/.rvm/gems/ruby-2.2.4/gems/rack-2.0.0.alpha/lib/rack/builder.rb:40:in
`parse_file'    from
/home/pd/.rvm/gems/ruby-2.2.4/gems/rack-2.0.0.alpha/lib/rack/server.rb:318:in
`build_app_and_options_from_config'     from
/home/pd/.rvm/gems/ruby-2.2.4/gems/rack-2.0.0.alpha/lib/rack/server.rb:218:in
`app'   from
/home/pd/.rvm/gems/ruby-2.2.4/gems/railties-5.0.0.beta1/lib/rails/commands/server.rb:56:in
`app'   from
/home/pd/.rvm/gems/ruby-2.2.4/gems/rack-2.0.0.alpha/lib/rack/server.rb:353:in
`wrapped_app'   from
/home/pd/.rvm/gems/ruby-2.2.4/gems/railties-5.0.0.beta1/lib/rails/commands/server.rb:134:in
`log_to_stdout'     from
/home/pd/.rvm/gems/ruby-2.2.4/gems/railties-5.0.0.beta1/lib/rails/commands/server.rb:74:in
`start'     from
/home/pd/.rvm/gems/ruby-2.2.4/gems/railties-5.0.0.beta1/lib/rails/commands/commands_tasks.rb:90:in
`block in server'   from
/home/pd/.rvm/gems/ruby-2.2.4/gems/railties-5.0.0.beta1/lib/rails/commands/commands_tasks.rb:85:in
`tap'   from
/home/pd/.rvm/gems/ruby-2.2.4/gems/railties-5.0.0.beta1/lib/rails/commands/commands_tasks.rb:85:in
`server'    from
/home/pd/.rvm/gems/ruby-2.2.4/gems/railties-5.0.0.beta1/lib/rails/commands/commands_tasks.rb:49:in
`run_command!'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/railties-5.0.0.beta1/lib/rails/command.rb:20:in
`run'   from
/home/pd/.rvm/gems/ruby-2.2.4/gems/railties-5.0.0.beta1/lib/rails/commands.rb:19:in
`<top (required)>'  from /home/pd/Documents/EventsApp/bin/rails:9:in
`require'   from /home/pd/Documents/EventsApp/bin/rails:9:in `<top
(required)>'    from
/home/pd/.rvm/gems/ruby-2.2.4/gems/spring-1.6.0/lib/spring/client/rails.rb:28:in
`load'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/spring-1.6.0/lib/spring/client/rails.rb:28:in
`call'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/spring-1.6.0/lib/spring/client/command.rb:7:in
`call'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/spring-1.6.0/lib/spring/client.rb:28:in
`run'   from
/home/pd/.rvm/gems/ruby-2.2.4/gems/spring-1.6.0/bin/spring:51:in `<top
(required)>'    from
/home/pd/.rvm/gems/ruby-2.2.4/gems/spring-1.6.0/lib/spring/binstub.rb:11:in
`load'  from
/home/pd/.rvm/gems/ruby-2.2.4/gems/spring-1.6.0/lib/spring/binstub.rb:11:in
`<top (required)>'  from /home/pd/Documents/EventsApp/bin/spring:13:in
`require'   from /home/pd/Documents/EventsApp/bin/spring:13:in `<top
(required)>'    from bin/rails:3:in `load'  from bin/rails:3:in `<main>'

Answer 1

The error is related to not having the correct ActionCable files in your project. You need app/channels/application_cable/channel.rb that looks like this

module ApplicationCable
  class Channel < ActionCable::Channel::Base
  end
end

and app/channels/application_cable/connection.rb

module ApplicationCable
  class Connection < ActionCable::Connection::Base
  end
end

Answer 2

If you upgraded from previous version (when actioncable was not in the bundle), check if config/application.rb contains

require "action_cable/engine"

Answer 3

I had the same problem when trying to use ActionCable with Rails 4.2.5 and the solution was to add the following to config/application.rb:

config.autoload_paths += %W(#{config.root}/app/channels)

This is with the ActionCable gem:

gem 'actioncable', github: 'rails/actioncable', branch: 'archive'

Answer 4

According to DHH's video tutorial from yesterday, there's an issue between Spring and an ActionCable dependency, so until the final release of Rails 5 you will need to recreate your project with the --skip-spring option.