Meta-programming for a fluent keyword.

fluent.rb

# Copyright (c) 2014 Mark Lanett.
# Permission is hereby granted, free of charge, to deal in this software without restriction of any sort.

module Fluent

  def self.included(base)
    base.extend(ClassSingletonMethods)
  end

  module ClassSingletonMethods
    def fluent(name, default = nil)
      ivar_ = ("@" + name.to_s).to_sym
      name_ = name.to_sym
      define_method(name_) do |*parameters|
        if parameters.size == 0
          if instance_variable_defined?(ivar_)
            instance_variable_get(ivar_)
          else
            value = default ? default.call : nil
            instance_variable_set(ivar_, value)
            value
          end
        else
          instance_variable_set(ivar_, parameters.first)
          self
        end
      end # define_method
    end # fluent
  end # ClassSingletonMethods

end # Fluent