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require 'concurrent/synchronization'
module Concurrent
module Collection
# A thread safe observer set implemented using copy-on-read approach:
# observers are added and removed from a thread safe collection; every time
# a notification is required the internal data structure is copied to
# prevent concurrency issues
#
# @api private
class CopyOnNotifyObserverSet < Synchronization::LockableObject
def initialize
super()
synchronize { ns_initialize }
end
# @!macro observable_add_observer
def add_observer(observer = nil, func = :update, &block)
if observer.nil? && block.nil?
raise ArgumentError, 'should pass observer as a first argument or block'
elsif observer && block
raise ArgumentError.new('cannot provide both an observer and a block')
end
if block
observer = block
func = :call
end
synchronize do
@observers[observer] = func
observer
end
end
# @!macro observable_delete_observer
def delete_observer(observer)
synchronize do
@observers.delete(observer)
observer
end
end
# @!macro observable_delete_observers
def delete_observers
synchronize do
@observers.clear
self
end
end
# @!macro observable_count_observers
def count_observers
synchronize { @observers.count }
end
# Notifies all registered observers with optional args
# @param [Object] args arguments to be passed to each observer
# @return [CopyOnWriteObserverSet] self
def notify_observers(*args, &block)
observers = duplicate_observers
notify_to(observers, *args, &block)
self
end
# Notifies all registered observers with optional args and deletes them.
#
# @param [Object] args arguments to be passed to each observer
# @return [CopyOnWriteObserverSet] self
def notify_and_delete_observers(*args, &block)
observers = duplicate_and_clear_observers
notify_to(observers, *args, &block)
self
end
protected
def ns_initialize
@observers = {}
end
private
def duplicate_and_clear_observers
synchronize do
observers = @observers.dup
@observers.clear
observers
end
end
def duplicate_observers
synchronize { @observers.dup }
end
def notify_to(observers, *args)
raise ArgumentError.new('cannot give arguments and a block') if block_given? && !args.empty?
observers.each do |observer, function|
args = yield if block_given?
observer.send(function, *args)
end
end
end
end
end
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