Metybur

A DDP client for Ruby to connect to Meteor apps.

Metybur lets your Ruby application connect to a Meteor app. It allows you to subscribe to collections and to receive updates on them. You can also call Meteor methods from Ruby.

Caution!

This gem isn't at version 1 yet and doesn't include basic features like proper error handling. Also only a subset of the DDP protocol is implemented so far. Everything described in this README should work, though.

I'll keep working on it constantly, so I suppose there will be a complete and stable version soon. Stay tuned!

Clemens

Installation

Add this line to your application's Gemfile:

gem 'metybur'

And then execute:

$ bundle

Or install it yourself as:

$ gem install metybur

Usage

Connecting to a Meteor app

Metybur runs in an EventMachine loop. Therefore all your code must be wrapped in an EM.run block.

require 'eventmachine'

EM.run do
  meteor = Metybur.connect('http://my-meteor-app.org:80/websocket')
end

will connect to your Meteor app. If you want to log in at your app, pass the credentials:

require 'eventmachine'

EM.run do
  meteor = Metybur.connect(
    'http://my-meteor-app.org:80/websocket',
    email:    'rubyist@meteor.com',
    password: 'twinkle twinkle'
  )
end

You can also pass a :username or :id instead of an :email. These arguments correspond to those described in the Meteor docs.

Alternatively you can log in at a later point by calling the login method explicitly:

require 'eventmachine'

EM.run do
  meteor = Metybur.connect('http://my-meteor-app.org:80/websocket')

  # Do something unauthenticated...

  meteor.login(user: {email: 'rubyist@meteor.com'}, password: 'twinkle twinkle'
end

From now on I'll skip the EM.run block in code examples, but don't forget about it. Otherwise it won't work! Promise!

Subscribing to a Meteor record set

After connecting to your Meteor app, you can subscribe to one of the published record sets:

meteor = Metybur.connect('http://my-meteor-app.org:80/websocket')
meteor.subscribe('my-chat-messages')

Subscription arguments can be passed right after the collection name:

meteor.subscribe('my-chat-messages', 10, channel: 'random')

Collections

Once you've subscribed, you will receive all records that are already in the record set. The record set contains records from one or more collections. You can process these records as they arrive:

@chat_messages = {}
meteor.collection('chat-messages')
  .on(:added) { |id, attributes| @chat_messages[id] = attributes }
  .on(:changed) { |id, attributes, cleared|
    chat_message = @chat_messages[id]
    chat_message.merge!(attributes)
    cleared.each { |field| chat_message.delete(field) }
  }
  .on(:removed) { |id| @chat_messages.delete(id) }

You can also assign multiple callbacks to one event:

@chat_messages = {}
collection = meteor.collection('chat-messages')

collection.on(:added) { |id, attributes| @chat_messages[id] = attributes }

collection.on(:added) { |id, attributes| puts "received message #{attributes[:text]}" }

Remote Procedure Calls

Call meteor methods to write back data to Meteor or to trigger actions in your Meteor app.

meteor.post_chat_message('Hey there!', in_room: 'General')

This corresponds to the following method call in Meteor:

// Javascript
Meteor.call('postChatMessage', ['Hey there!', { inRoom: 'General' }]);

Methods and hash keys will be camel-cased for you, so you can stick to the Ruby naming convention.

If you prefer the Meteor syntax, you can also call the method like this:

meteor.call('postChatMessage', inRoom: 'General')

Note that you have to choose this syntax, if your Meteor method name collides with a Metybur method (like collection or subscribe).

Results

Since methods are executed asynchronously, they won't return a result immediately:

# Doesn't work!
messages = meteor.chat_messages(in_room: 'General')
messages.each { |message| puts message }

Instead, pass a block to the method. The block will get called once the result arrives.

meteor.chat_messages(in_room: 'General') do
  result.each { |message| puts message }
end

Errors

Your meteor methods might throw errors, or the method you call might not even exist. You can rescue these errors right in the method's result block:

meteor.chat_messages(in_room: 'General') do
  begin
    result.each { |message| puts message }
  rescue Metybur::MethodError => e
    puts "An error ocurred: #{e}"
  end
end

Note that the error is raised by the result. If your method doesn't return a result, you can still handle the error:

meteor.post_chat_message('Hey there!', in_room: 'General') do
  begin
    raise_errors
  rescue Metybur::MethodError => e
    puts "An error ocurred: #{e}"
  end
end

Logging

To debug your application, you can lower the log level to see all incoming websocket messages.

Metybur.log_level = :debug

Make sure to set the log level before calling Metybur.connect, as it won't have any effect afterwards.

Reconnecting

When the websocket connection is lost, Metybur will try to reconnect to your Meteor app. After the reconnect the login method is called and all your subscriptions are subscribed again.

This means in particular that all documents get sent again and therefore all your collections' added callbacks will get triggered again.

Contributing

1. Fork it ( https://github.com/clemenshelm/metybur/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request