class Webgen::Blackboard

A blackboard object provides methods for inter-object communication. Objects may register themselves for specific messsage names and get notified when such a message gets dispatched.

For a list of all available messages have a look at the Webgen documentation page.

Public Class Methods

new() click to toggle source

Create a new Blackboard object.

# File lib/webgen/blackboard.rb, line 11
def initialize
  @listener = {}
end

Public Instance Methods

add_listener(msg_name, id = nil, position = {}, &block) click to toggle source

Add the given block as listener for the message msg_name.

The id parameter can be used to specify a string which uniquely identifies the listener.

The position parameter can be used to specify where the listener should be added. The keys :before and :after are recognized and must contain a valid listener ID. If no key is or an unknown ID is specified, the listener is added as last entry in the listener array.

# File lib/webgen/blackboard.rb, line 22
def add_listener(msg_name, id = nil, position = {}, &block)
  position = if position[:before]
               (@listener[msg_name] || []).index {|lid, obj| lid == position[:before]}
             elsif position[:after]
               (pos = (@listener[msg_name] || []).index {|lid, obj| lid == position[:after]}) && pos + 1
             end
  insert_listener_at_position(msg_name, id, position || -1, &block)
end

dispatch_msg(msg_name, *args) click to toggle source

Dispatch the message msg_name to all listeners for this message, passing the given arguments.

# File lib/webgen/blackboard.rb, line 50
def dispatch_msg(msg_name, *args)
  return unless @listener[msg_name]
  @listener[msg_name].each {|id, obj| obj.call(*args)}
end

remove_listener(msg_names, id) click to toggle source

Remove the blocks associated with the given ID from the dispatcher queues of the given message names.

# File lib/webgen/blackboard.rb, line 44
def remove_listener(msg_names, id)
  [msg_names].flatten.each {|name| @listener[name].delete_if {|lid, b| lid == id} if @listener[name]}
end

Private Instance Methods

insert_listener_at_position(msg_name, id, position, &block) click to toggle source

Insert the block as listener for msg_name with the given id at the position in the listener array.

# File lib/webgen/blackboard.rb, line 33
def insert_listener_at_position(msg_name, id, position, &block)
  if !block.nil?
    (@listener[msg_name] ||= []).insert(position, [id, block])
  else
    raise ArgumentError, "You have to provide a block"
  end
end