From: Jason Lillywhite <jason.lillywhite@...>
Date: 2009-06-26T23:49:49+09:00
Subject: question about using the Factory Pattern

I'm trying to create a method that returns a new object of the same
class it is in. Here is my code (for doing a simple unit conversion from
any length units to meters):

class Unit
  def initialize(n)
    @unit = n[/[a-z]+/]
    @value = n.to_f
  end

  def conversion_factor(unit)
    #... converts to base units, meters for now
  end

  def base
    new_n = (@value * conversion_factor(@unit)).to_s + " m"
  end
end

So I can do n1 = Unit.new('5 ft')

Then n1.base will return the string "1.523999 m"

But what I want is for that to automatically become one of my Unit
objects, not just a string.

I was told I could use the factory pattern -

class FactoryClass
def self.create_object(params)
FactoryClass.new(params)
end
end

but I can't put it together. Could someone give me a hint? Thank you!
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