vendor/rails/activesupport/lib/active_support/core_ext/module/synchronization.rb

   1 class Module
   2   # Synchronize access around a method, delegating synchronization to a
   3   # particular mutex. A mutex (either a Mutex, or any object that responds to
   4   # #synchronize and yields to a block) must be provided as a final :with option.
   5   # The :with option should be a symbol or string, and can represent a method,
   6   # constant, or instance or class variable.
   7   # Example:
   8   #   class SharedCache
   9   #     @@lock = Mutex.new
  10   #     def expire
  11   #       ...
  12   #     end
  13   #     synchronize :expire, :with => :@@lock
  14   #   end
  15   def synchronize(*methods)
  16     options = methods.extract_options!
  17     unless options.is_a?(Hash) && with = options[:with]
  18       raise ArgumentError, "Synchronization needs a mutex. Supply an options hash with a :with key as the last argument (e.g. synchronize :hello, :with => :@mutex)."
  19     end
  20
  21     methods.each do |method|
  22       aliased_method, punctuation = method.to_s.sub(/([?!=])$/, ''), $1
  23
  24       if method_defined?("#{aliased_method}_without_synchronization#{punctuation}")
  25         raise ArgumentError, "#{method} is already synchronized. Double synchronization is not currently supported."
  26       end
  27
  28       module_eval(<<-EOS, __FILE__, __LINE__)
  29         def #{aliased_method}_with_synchronization#{punctuation}(*args, &block)
  30           #{with}.synchronize do
  31             #{aliased_method}_without_synchronization#{punctuation}(*args, &block)
  32           end
  33         end
  34       EOS
  35
  36       alias_method_chain method, :synchronization
  37     end
  38   end
  39 end