Activerecord conditions and named scope - undefined method `created_at'

Subscriber  
has_and_belongs_to_many :skills. 

Skill   
has_many :positions

in subscriber.rb:

scope :notify_today, 
      includes(:skills => :positions).
 开发者_如何学Python     where("positions.created_at > ? AND positions.created_at > ?", 
             1.day.ago, self.created_at)

Basically I want to find all subscribers that have positions 1) created 1.day.ago AND 2) created after the subscriber

---

The error occurs because the class of self here is Class, not Subscriber, as is wanted.

As a solution, you can make a lamda like this and pass in the parameter for created_at: (I presume your scope is working otherwise, because I have not tested this with your scope code specifically)

scope :notify_today, 
      lambda { |created_at| includes(:skills => :positions).
      where("positions.created_at > ? AND positions.created_at > ?", 
             1.day.ago, created_at) }

And use it:

@subscribers = notify_today(Time.now)