How do I create a class instance from a string name in ruby?

Question

I have the name of a class and I want to create an instance of that class so that I can loop through each rails attribute that is present in the schema of that class.

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Answer 1

module One
  module Two
    class Three
      def say_hi
        puts "say hi"
      end
    end
  end
end

one = Object.const_get "One"

puts one.class # => Module

three = One::Two.const_get "Three"

puts three.class # => Class

three.new.say_hi # => "say hi"

In ruby 2.0 and, possibly earlier releases, Object.const_get will recursively perform a lookup on a namespaces like Foo::Bar. The example above is when the namespace is known ahead of time and highlights the fact that const_get can be called on modules directly as opposed to exclusively on Object.