如何在活動記錄中加入has_many與範圍的關聯？

Question

這是我的聯想和範圍設置：

has_many :owned_products 

has_many :owned_lessons, :through => :owned_products, :source => :lesson, :conditions => "owned_products.product_type = 'Lesson'" 

scope :active_purchase_scope, lambda { 
    where('owned_products.created_at' => (Date.today - CONFIG['downloads']['time_window'].days)..(Date.today)).order('owned_products.created_at DESC') 
} 

def active_lessons 
    owned_lessons.active_purchase_scope 
end 

這是錯誤我得到：

ruby-1.8.7-p334 :005 > User.find_by_username('joeblow').active_lessons 
NoMethodError: undefined method `active_purchase_scope' for #<User:0x1051a26c8> 

達

Answer 1

一個scope可以被看作是一個類的方法和association可作爲實例方法處理。在您的代碼示例中，owned_lessons方法返回一個數組對象。您不能在數組對象（或用戶對象）上調用active_purchase_scope，因爲範圍只能在Model類上調用（即您的情況爲User.active_purchase_scope）

您可以通過在範圍上添加範圍來解決此問題該Lesson模型

class Lesson 
    has_many :owned_products 

    scope :active_purchase_scope, lambda { 
    include(::owned_products).where('owned_products.created_at' => 
      (Date.today - CONFIG['downloads']['time_window'].days)..(Date.today)). 
      order('owned_products.created_at DESC') 
    } 

end 

並改寫User類如下：

class User 

    has_many :owned_products 

    has_many :owned_lessons, :through => :owned_products, :source => :lesson, 
       :conditions => "owned_products.product_type = 'Lesson'" 


    def active_lessons 
    owned_lessons.active_purchase_scope 
    end 

end 

的owned_lessons返回上Lesson模型匿名的範圍，因此我們可以用S IT連鎖從相同的模型應付active_purchase_scope。