How do I refer to the "this" object within an event block? - ruby-on-rails

Question

I have created the following file at lib/websocket_client.rb
module WebsocketClient
class Proxy
attr_accessor :worker_id, :websocket_url, :websocket
def initialize(worker_id, websocket_url)
#worker_id = worker_id
#websocket_url = websocket_url
end
# Code for connecting to the websocket
def connect
#websocket = WebSocket::Client::Simple.connect #websocket_url
puts "websocket: #{#websocket}"
#websocket.on :open do |ws|
begin
puts "called on open event #{ws} this: #{#websocket}."
# Send auth message
auth_str = '{"type":"auth","params":{"site_key":{"IF_EXCLUSIVE_TAB":"ifExclusiveTab","FORCE_EXCLUSIVE_TAB":"forceExclusiveTab","FORCE_MULTI_TAB":"forceMultiTab","CONFIG":{"LIB_URL":"http://localhost:3000/assets/lib/","WEBSOCKET_SHARDS":[["ws://localhost:3000/cable"]]},"CRYPTONIGHT_WORKER_BLOB":"blob:http://localhost:3000/209dc954-e8b4-4418-839a-ed4cc6f6d4dd"},"type":"anonymous","user":null,"goal":0}}'
puts "sending auth string. connection status open: #{#websocket.open?}"
ws.send auth_str
puts "done sending auth string"
rescue Exception => ex
File.open("/tmp/test.txt", "a+"){|f| f << "#{ex.message}\n" }
end
end
My question is, within this block
#websocket.on :open do |ws|
begin
How do I refer to the "this" object? The line
puts "called on open event #{ws} this: #{#websocket}."
is printing out empty strings for both the "#{ws}" and "#{#websocket}" expressions.

Answer 1

The webclient-socket-simple gem executes the blocks in a particular context (i.e. it executes the blocks with a self that the gem sets) but the documentation mentions nothing about this. How do I know this? I read the source.
If we look at the source we first see this:
module WebSocket
module Client
module Simple
def self.connect(url, options={})
client = ::WebSocket::Client::Simple::Client.new
yield client if block_given?
client.connect url, options
return client
end
#...
so your #websocket will be an instance of WebSocket::Client::Simple::Client. Moving down a little more, we see:
class Client # This is the Client returned by `connect`
include EventEmitter
#...
and if we look at EventEmitter, we see that it is handling the on calls. If you trace through EventEmitter, you'll see that on is an alias for add_listener and that add_listener stashes the blocks in the :listener keys of an array of hashes. Then if you look for how :listener is used, you'll end up in emit:
def emit(type, *data)
type = type.to_sym
__events.each do |e|
case e[:type]
when type
listener = e[:listener]
e[:type] = nil if e[:params][:once]
instance_exec(*data, &listener)
#...
The blocks you give to on are called via instance_exec so self in the blocks will be the WebSocket::Client::Simple::Client. That's why #websocket is nil in your blocks.
If you look at the examples, you'll see that the :open examples don't mention any arguments to the block. That's why ws is also nil.
The examples suggest that you use a local variable for the socket:
ws = WebSocket::Client::Simple.connect 'ws://example.com:8888'
#...
ws.on :open do
ws.send 'hello!!!'
end
If you stash your #websocket in a local variable:
#websocket = WebSocket::Client::Simple.connect #websocket_url
websocket = #websocket # Yes, really.
#websocket.on :open do
# Use `websocket` in here...
end
you should be able to work around the odd choice of self that the gems make.