add_class_method_to.rb

# Assumes ruby 1.9

# klass is expected to be a constant as a string or an actual constant
def add_method_to klass, meffod_name, &meffod_body
  # Make sure we have a constant to work against
  klass = klass.split("::").inject(Kernel) {|parent, k| parent.const_get(k) } if String === klass
  # Add the method to the singleton class of our constant (class level method)
  klass.singleton_class.__send__(:define_method, meffod_name.to_sym, &meffod_body)
end

class Foo
  class Bar
  end
end


Foo.respond_to?(:blah) # => false
add_method_to Foo, :blah do
  :blah
end
Foo.respond_to?(:blah) # => true
Foo.blah # => :blah

Foo.respond_to?(:sed) # => false
add_method_to "Foo", :sed do
  :sed
end
Foo.respond_to?(:sed) # => true
Foo.sed # => :sed

Foo::Bar.respond_to?(:fred) # => false
add_method_to Foo::Bar, :fred do
  :fred
end
Foo::Bar.respond_to?(:fred) # => true
Foo::Bar.fred # => :fred

Foo::Bar.respond_to?(:george) # => false
add_method_to "Foo::Bar", :george do
  :george
end
Foo::Bar.respond_to?(:george) # => true
Foo::Bar.george # => :george