How to use websockets in Rails - ruby

Question

I'm trying to integrate web sockets into my Rails application as per this link: https://github.com/websocket-rails/websocket-rails/wiki/Installation-and-Setup
I use Ruby 2.0 and Rails3.
The contents of the relevant files:
Gemfile:
gem 'websocket-rails
events.rb
WebsocketRails::EventMap.describe do
subscribe :awesomeness_approval, :to => ChatController, :with_method => :awesomeness_approval
end
development.rb
...
config.middleware.delete Rack::Lock
...
chat_controller.rb
class ChatController < WebsocketRails::BaseController
def initialize_session
# perform application setup here
controller_store[:message_count] = 0
end
def awesomeness_approval
if message[:awesomeness] > 5
trigger_success {:m => 'awesome level is sufficient'}
else
trigger_failure {:m => 'awesome level is insufficient'}
end
end
end
chat.js
var dispatcher = new WebSocketRails('localhost:3000/websocket');
dispatcher.on_open = function(data) {
console.log('Connection has been established: ', data);
}
var success = function(response) {
console.log("You are awesome because: "+response.message);
}
var failure = function(response) {
console.log("You are not very awesome because: "+response.message);
}
var message = { awesomeness: 4 }
dispatcher.trigger('awesomeness_approval', message, success, failure);
When I try to start rails server, I get the following error:
w/app/controllers/chat_controller.rb:9: syntax error, unexpected =>, expecting '}' (SyntaxError)
trigger_success {:m => 'awesome level is sufficient'}
...
/app/controllers/chat_controller.rb:11: syntax error, unexpected =>, expecting '}'
trigger_failure {:m => 'awesome level is insufficient'}
However, if I comment out the above lines, I'm able to start the server, and the browser is able to connect to the web socket. The following output is seen on browser console:
"Connection has been established: " Object { connection_id: "f66c4298eb103312e181" } chat.js:3
Please help.

Answer 1

Your error comes from a syntax ambiguity in your method call.
When you write
trigger_success {:m => 'awesome level is sufficient'}
the opening curly brace is interpreted to be the start of a block argument to the method. However, you intend it to be a hash. Interpreted as a block, it would indeed be wrong syntax as a block doesn't allow a simple hash rocket.
You can resolve this ambiguity, you can use parenthesis:
trigger_success({:m => 'awesome level is sufficient'})
That way, it is clear for the ruby parser that you actually mean to pass a single hash argument to the method and is currently parsed.