method_missing override is not working

Answer 1

When you run MyObject.first.tail the object that actually responds is an AssociationProxy class that

has most of the basic instance methods removed, and delegates # unknown methods to @target via method_missing

You can get more details about the proxy running:

MyObject.first.proxy_owner
MyObject.first.proxy_reflection
MyObject.first.proxy_target

If you look in the code, you can see that the AssociationProxy proxies the method some_method_in_base to your MyState class only if MyState responds to *some_method_in_base* as you can see in the code below.

  private
    # Forwards any missing method call to the \target.
    def method_missing(method, *args, &block)
      if load_target
        if @target.respond_to?(method)
          @target.send(method, *args, &block)
        else
          super
        end
      end
    end

Therefore, the method_missing you have defined in the target class is never called.