Ruby Magic: Metaprogramming

Rails, if you’ve used it, has a rather elegant way of manipulating time. Stuff like 1.hours and 2.minutes.from_now just work. Let’s see how Ruby modules can be extended really really easily:

#! /usr/bin/env ruby

class Integer
  def seconds
    self
  end

  def minutes
    seconds * 60
  end

  def hours
    minutes * 60
  end

  def days
    hours * 24
  end

  def months
    days * 30
  end

  def years
    months * 12
  end

  def from_now
    Time.now + self
  end

  def before
    Time.now - self
  end
end

class String
  def palindrome?
    self == self.reverse
  end
end

class Time
  def leap_year?
    (year % 4).zero? and ((not (year % 100).zero?) or (year % 1000).zero?)
  end
end

class TrueClass
  def say
    "is"
  end
end

class FalseClass
  def say
    "is not"
  end
end

#2 is an Integer
puts 2.minutes.from_now

#"vishnu" is a String
puts "vishnu".palindrome?
puts "malayalam".palindrome?

puts 2.years.from_now.leap_year?

#Check if n years before is a leap year
puts "How many years before?"
year = Integer(readline)
puts "#{Time.now.year - year} #{year.years.before.leap_year?.say} a leap year."

The interesting thing about Ruby is not that metaprogramming is possible, but Ruby makes it really easy to do it.

Published by vishnugopal

Vishnu Gopal is an Anime fanatic, World of Warcraft player, SciFi nut, hopeless romantic & CTO at SV.CO.

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