Streamlined Modeling Examples

gistfile1.rb

class User < ActiveRecord::Base
  # Collaboration Rules
  def can_like?(like)
    user.plugins.include?(:page_like)
  end

  # Business Service
  def like(page)
    Like.create!(:page => page, :user => self)
  end
end

class Page < ActiveRecord::Base
  # Collaboration Rules
  def likable?(like)
    # this could be overridden in a subclasses
    true
  end
end

class Like < ActiveRecord::Base
  belongs_to :user
  belongs_to :page

  validate :user_can_like?, :page_is_likeable?

  private

  def user_can_like?
    if user && !user.can_like?(self)
      errors.add(:user, "does not have permission to like")
    end
  end

  def page_is_likeable?
    if page && !page.likeable?(self)
      errors.add(:page, "cannot be liked")
    end
  end
end