written by Britt Selvitelle

Programmatically Naming and Creating Variables with Ruby

This has been covered elsewhere. I did it in the past, but of course life has a way of kicking out old info to make space for the new.

Without being too terribly long winded, I will say that the reason for making this post is due to the fact that when I wanted to figure out how to dynamically create variables with ruby, I did a google search for a number of derivations of: ruby programmatically creating variables. This came up with a lot of nothing. I quickly realized this was turning into one of those dreaded cases of having to know the method name you’re looking for before you can find it. I’m a bit embarrassed to say I didn’t check this one, but thanks to blink on #ruby-lang, I’m posting just incase someone else searches with the same terms.

So at its very simplest:

  eval "ans = 42"

Read more about eval at Jim Weirich’s always excellent blog.

Furthermore, instance variables of a class can be set via set_instance_variable.

class DeepThought
end

question = DeepThought.new
question.instance_variable_set("@ans", 42)

def question.what_is_the_answer
  return @ans
end

question.what_is_the_answer
=> 42