Originally I went through Metaprogramming Ruby about a year ago, but never really took the time to use it. Recently I’ve been doing much more Ruby, so I feel like it is time for a refresher.

Ruby is a really interesting programming language. Very recently, my view shifted on it. For a long time, I wasn’t sure exactly what to think about it. Now, Ruby seems like the ideal scripting language to interact with the Unix environment… especially because I am really sick of dealing with Bash.

So, here is a first in a series of examples that show off the great dynamic features of Ruby. These examples are

Most of what makes Ruby different is only surprising from the standpoint of a user of “mainstream” languages. To a Lisp programmer, for example, none of these should be very surprising.

Eventually, I’m going to investigate adding real syntactic extensions (macros), but that is for a future date. There are obvious ways to approach this, and libraries that basically do it (rewrite ruby, etc), but there doesn’t seem to be much action in this arena. Which is a shame. I think this is important for the long-term health of Ruby. I believe the perception (and reality) of Ruby as an advanced language is important for its long term health.

So, here we go: a basic set of minispec specs which demonstrate some extreme flexibility of Ruby:

describe "ruby classes" do

  describe "definitions are just regular code" do

    it "evaluates regular code" do
      $the_secret = nil

      class ClassDefSideEffects
        $the_secret = "shh"
      end

      $the_secret.must_equal "shh"
    end

    it "return what was last evaluated" do
      (class Doot
         1 + 1
       end).must_equal 2
    end
  end


  describe "classes are objects" do
    it "has methods (such as class) and reports that it has the type class" do
      class Dootz; end
      Dootz.class.must_equal Class
    end
  end

  describe "dynamically creating classes" do
    it "can create new classes" do
      x = Class.new
      y = x.new
      z = x.new

      y.class.must_equal z.class

      y.class.must_equal x
    end

    it "is just objects, so can be passed around" do
      class Dootz; end

      x = Dootz.class.new.new

      x.class.class.must_equal Class
    end
  end
end

Next time we’ll get into blocks. That way, we can cover the rest of the sweet things that can be done with the ruby object model.