Question

I’m trying to write a program that dynamically defines ruby classes based on configuration read from a file. I know I can use Class.new to do this. Here’s an example program:

x = [1,2,3]

Test = Class.new do
  @@mylist = x

  def foo
    puts @@mylist
  end
end

Test.new.foo

When I run this I get the following output (running with ruby 1.9.3p0):

c:/utils/test.rb:4: warning: class variable access from toplevel
c:/utils/test.rb:7: warning: class variable access from toplevel
1
2
3

Does anyone know what causes these warnings and how I can get rid of them?

I’ve tried replacing the line tjhat does

@@mylist = x

with this

class_variable_set(:@@mylist, x)

But when I do that I get this error instead:

c:/utils/test.rb:7: warning: class variable access from toplevel
c:/utils/test.rb:7:in `foo': uninitialized class variable @@mylist in Object (NameError)
        from c:/utils/test.rb:11:in `'

Thanks in advance!

Answer 1

Just to remove this warning, you should use class_variable_set method:

x = [1,2,3]

Test = Class.new do
  class_variable_set(:@@mylist, x)

  def foo
    puts @@mylist
  end
end