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#--
#
# Author:: Nathaniel Talbott.
# Copyright:: Copyright (c) 2000-2002 Nathaniel Talbott. All rights reserved.
# License:: Ruby license.
require 'test/unit/util/procwrapper'
module Test
module Unit
module Util
# This is a utility class that allows anything mixing
# it in to notify a set of listeners about interesting
# events.
module Observable
# We use this for defaults since nil might mean something
NOTHING = "NOTHING/#{__id__}"
# Adds the passed proc as a listener on the
# channel indicated by channel_name. listener_key
# is used to remove the listener later; if none is
# specified, the proc itself is used.
#
# Whatever is used as the listener_key is
# returned, making it very easy to use the proc
# itself as the listener_key:
#
# listener = add_listener("Channel") { ... }
# remove_listener("Channel", listener)
def add_listener(channel_name, listener_key=NOTHING, &listener) # :yields: value
unless(block_given?)
raise ArgumentError.new("No callback was passed as a listener")
end
key = listener_key
if (listener_key == NOTHING)
listener_key = listener
key = ProcWrapper.new(listener)
end
channels[channel_name] ||= {}
channels[channel_name][key] = listener
return listener_key
end
# Removes the listener indicated by listener_key
# from the channel indicated by
# channel_name. Returns the registered proc, or
# nil if none was found.
def remove_listener(channel_name, listener_key)
channel = channels[channel_name]
return nil unless (channel)
key = listener_key
if (listener_key.instance_of?(Proc))
key = ProcWrapper.new(listener_key)
end
if (channel.has_key?(key))
return channel.delete(key)
end
return nil
end
# Calls all the procs registered on the channel
# indicated by channel_name. If value is
# specified, it is passed in to the procs,
# otherwise they are called with no arguments.
#
#--
#
# Perhaps this should be private? Would it ever
# make sense for an external class to call this
# method directly?
def notify_listeners(channel_name, *arguments)
channel = channels[channel_name]
return 0 unless (channel)
listeners = channel.values
listeners.each { |listener| listener.call(*arguments) }
return listeners.size
end
private
def channels
@channels ||= {}
return @channels
end
end
end
end
end
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