Hyperloop uses Policies to regulate what connections are opened between clients and the server and what data is distributed over those connections.

Policy Classes

Policies are defined through policy classes:

class UserPolicy # defines policies for the User class
  # The regulate_instance_connections method enables instances of the User
  # class to be treated as a channel.

  # The policy is defined by a block that is executed in the context of the
  # current acting_user.

  # For our User instance connection the policy is that there must be a
  # logged-in user and the connection is made to that user:
  regulate_instance_connections { self }
  # If there is no logged in user self will be nil, and no connection will be
  # made.

class TeamPolicy # defines policies for the Team class
  # Users can only connect to Teams that they belong to
  regulate_instance_connections { teams }

class AdminUserPolicy
  # All AdminUsers share the same connection so we setup a class wide
  # connection available to any users who are admins.
  regulate_class_connection { admin? }

  # The AdminUser channel will receive all attributes
  # of all records, unless the attribute is named :password
  regulate_all_broadcasts do |policy|

class TodoPolicy
  # Policies can be established for models that are not channels as well.

  # The regulate_broadcast method will describe what attributes to send
  # when a Todo model changes.

  # The blocks of broadcast policies run in the context of the changed model
  # so we have access to all the model's methods.  In this case Todo
  # belongs to a Team through the 'team' relationship.
  regulate_broadcast do |policy|
    # send all Todo attributes to the todo's team channel

class MessagePolicy
  # Broadcast policies can be arbitrarily complex.  In this case we
  # want to broadcast the entire message to the sender and the
  # recipient's instance channels.
  # In addition if the message is not private, then we want to send to all
  # the team instance channels that are shared between the sender and
  # recipient's teams.
  regulate_broadcast do |policy|
    policy.send_all.to(sender, recipient)
    policy.send_all.to(sender.teams.merge(recipient.teams)) unless private?

That concludes this introduction to Hyperloop, but before you go on to our Tutorials or Docs, please read the next section where we describe our pragmatic approach to architecture.