class CallForParticipation < ActiveRecord::Base belongs_to :conference def open! self.opens_at = Time.now unless self.opens_at.present? self.closes_at = nil save end def close! self.closes_at = Time.now save end def open? self.opens_at.present? and self.opens_at < Time.now end def closed? self.closes_at.present? and self.closes_at < Time.now end def in_progress? open? and not closed? end end