def_class

        # ERB.def_class

(from ruby core)
---
    def_class(superklass=Object, methodname='result')

---

Define unnamed class which has *methodname* as instance method, and
return it.

example:
    class MyClass_
      def initialize(arg1, arg2)
        @arg1 = arg1;  @arg2 = arg2
      end
    end
    filename = 'example.rhtml'  # @arg1 and @arg2 are used in example.rhtml
    erb = ERB.new(File.read(filename))
    erb.filename = filename
    MyClass = erb.def_class(MyClass_, 'render()')
    print MyClass.new('foo', 123).render()