Dynamically adding class methods

dynamic_class.rb

# I want to add DynamicClass.some_method, not DynamicClass.new.some_method, so..

class DynamicClass
  @@syms = []
  def self.metaclass
    class << self; self; end
  end
  def self.add_method(sym)
    @@syms.push(sym) unless @@syms.include?(sym)
    metaclass.instance_eval do
      define_method(sym) do |*p|
        yield(*p) if block_given?
      end
    end
  end
  def self.remove_method(sym)
    @@syms.delete(sym)
    metaclass.instance_eval do
      remove_method(sym)
    end
  end
  def self.remove_methods!
    @@syms.dup.each{|sym| remove_method(sym)}
    @@syms = []
  end
end

class Foo < DynamicClass; end

def test
  Foo.add_method(:delete) {|id| id}
  Foo.delete('bar')
end

puts test

Didn't see what you were going for in my first comment, my fault. Maybe something like this?

class DynamicClass
end

class Foo < DynamicClass; end

Foo.respond_to? :bar # => false
DynamicClass.respond_to? :bar # => false

class Foo
  superclass.instance_eval do
    def bar
      'woot!'
    end
  end
end

Foo.respond_to? :bar # => true
DynamicClass.respond_to? :bar # => true

class Foo
  instance_eval do
    undef :bar
  end
end

Foo.respond_to? :bar # => false
DynamicClass.respond_to? :bar # => true

Hey, thanks for checking this out! The thing is that I wanted to be able to add and remove methods during test runs. As far as I know you can't open up a class whilst you're inside a method. The gist sort-of works, but currently suffers from the fact that the @@syms variable is shared by all classes that extend Dynamic class. This was just an experiment in making a small class mocking utility.