Adding an instance variable to a class in Ruby

Question

How can I add an instance variable to a defined class at runtime, and later get and set its value from outside of the class?

I\'m looking for a metaprogramming so

Answer 1

I wrote a gem for this some time ago. It's called "Flexible" and not available via rubygems, but was available via github until yesterday. I deleted it because it was useless for me.

You can do

class Foo
    include Flexible
end
f = Foo.new
f.bar = 1

with it without getting any error. So you can set and get instance variables from an object on the fly. If you are interessted... I could upload the source code to github again. It needs some modification to enable

f.bar?
#=> true

as method for asking the object if a instance variable "bar" is defined or not, but anything else is running.

Kind regards, musicmatze