Class: Webgen::Blackboard

Inherits:
Object
  • Object
show all
Defined in:
lib/webgen/blackboard.rb

Overview

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.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Blackboard

Create a new Blackboard object.



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# File 'lib/webgen/blackboard.rb', line 12

def initialize
  @listener = {}
end

Instance Method Details

#add_listener(msg_name, id = nil, position = {}, &block) ⇒ Object

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.



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# File 'lib/webgen/blackboard.rb', line 23

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) ⇒ Object

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



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# File 'lib/webgen/blackboard.rb', line 51

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) ⇒ Object

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



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# File 'lib/webgen/blackboard.rb', line 45

def remove_listener(msg_names, id)
  [msg_names].flatten.each {|name| @listener[name].delete_if {|lid, b| lid == id} if @listener[name]}
end