I've ran into the same problem before, and the way that I handled it was

class Foo < ActiveRecord::Base
  belongs_to :system

  class Entity < Grape::Entity
    expose :system do |foo, options|
      foo.system
    end
  end
end

It's not great, but it works.

Is there something we can do about this in grape-entity?

Sure, setting this to false. But there's a spec testing specifically for this, so I guess you guys were presented with a use case for allowing private methods of the Entity to take priority over the delegator's attribute.

You could also just exclude methods not owned by the entity class, á la

def delegate_attribute attribute
  if respond_to?(attribute, true) && method(attribute).owner == self.class
   ...

@Linell Thanks, that would work. Unfortunately, we actually do not have the Entity classes in the model classes themselves (gave that example for simplicity), so we usually have something like

module Entities
  class Foo < Grape::Entity
    expose :system, using: Entities::System
  end
end