From: Wyss Clemens <WYS@...>
Date: 2001-05-19T15:37:44+09:00
Subject: [ruby-talk:15391] PROPOSAL: Java-like method-based synchronization mechanism in Rub	y

Hi all,
the synchronized-call (in class Demo) in the following code-snippet:

require �synchronized�

class Demo

  def method1()
    ...
  end

  def method2()
    ...
  end

  synchronized (:test1)
end

ensures that method1-calls are synchronized, whereas method2-calls are not.

Find attached a pure ruby-solution (synchronized.rb):
---------
require 'thread'

class Module
  def synchronized(*methods)
    if methods.size() > 0 then
      # we need a Mutex (-getter)
      module_eval  <<-EOS
      def __mutex__()
	if (@__mutex__.nil?()) then 
	  @__mutex__ = Mutex.new() 
	end 
	return @__mutex__
      end
      EOS
    end
    methods.each { | method |
      synchronizeMethod(method.to_s())
    }
  end # synchronize(*methods)
  private
  def synchronizeMethod(method)
    # make a "copy" of the original method
    instance_eval("alias_method(:__#{method}__, :#{method})")
    # now create the "synchronized" wrapper method
    module_eval <<-EOS 
    def #{method}(*args)  
      __mutex__().synchronize { 
	#print 'SYNCHRONIZED CALL'; 
	if args == [] then 
	  __#{method}__() 
	else 
	  __#{method}__(args) 
	end 
      } 
    end
    EOS
    
  end # synchronizeMethod(method)
end
---------
Note: �synchronized� is to be applied in the same manner as �attr_reader�,
�attr_writer�, etc.
Any comments, improvements?
Something for the RAA?
Enjoy the weekend.
Clemens