In rails you can just do:
clazz = 'ExampleClass'.constantize
In pure ruby:
clazz = Object.const_get('ExampleClass')
with modules:
module Foo
class Bar
end
end
you would use
> clazz = 'Foo::Bar'.split('::').inject(Object) {|o,c| o.const_get c}
=> Foo::Bar
> clazz.new
=> #<Foo::Bar:0x0000010110a4f8>