Satish’s Blog

I have a singleton method in one of my service calls which I wanted to have memoize functionality. While there are several ways to do, I wanted to have a simple elegant way to do it. I have seen an example from Dave Thomas for instance methods. This one is similar to one of his examples but works for singleton methods. Comments are welcome.

module CacheHelper
  def cache(name)
    eigen_class = class << self
      self
    end
    eigen_class.instance_eval do
      memory = {}
      original = "original#{name}"
      alias_method(original, name)
      define_method(name) do |*args|
        if memory.has_key?(args)
          memory[args]
        else
          memory[args] = send original, *args
        end
      end
    end
  end
end

I am working on rails application that talks to legacy oracle database. The id columns are named as oid and they are of number type. The emulate_integers_by_column_name attribute in oracle enhanced driver allows us to set this attribute to true, to change the type of id columns to fixnum. I wrote this code to override and work for columns with oid in its name. All you need to do is put it in a separate file in initializers directory and off you go it works..

ActiveRecord::ConnectionAdapters::OracleEnhancedAdapter.emulate_integers_by_column_name = true

ActiveRecord::ConnectionAdapters::OracleEnhancedAdapter.instance_eval do
  def is_integer_column?(name)
      name =~ /(^|_)oid$/i
  end
end

I could not find a good example of using ruby hessian api. Here is a sample code that I wrote at my work place.
Hope this helps.

require 'hessian'
class Person

@@client = Hessian::HessianClient.new('url')

class << self

    def find arg

      new(@@client.method(arg))

    end

  end

def initialize(hash)

    hash.each do |k,v|

      self.instance_variable_set("@#{k}", v)

      self.class.send(:define_method, k, proc{self.instance_variable_get("@#{k}")})

      self.class.send(:define_method, "#{k}=", proc{|v| self.instance_variable_set("@#{k}", v)})

    end

  end

end

p = Person.find('obama')