升级到Rails 3中，联想的has_many扩展不再与范围的工作

Question

我升级轨2.3应用轨3.0.3

我有我的Product模型下面的联想扩展和范围

has_many :related_products, :through => :product_related_products do 
    [:alternative, :complement, :bigger_pack, :higher_quantity, :lower_quality].each do |meth| 
    define_method(meth) { 
     find :all, :conditions => ["product_related_products.#{meth} = ?", true] } 
    end 
end 

scope :visible, where(:hidden => false) 

取自概念：http://guides.rubyonrails.org/association_basics.html#association-extensions

当我调用链关联

@product.related_products.visible.alternative 

它可以在导轨2.3罚款，我得到了在Rails 3的以下错误：

undefined method `alternative' for #<ActiveRecord::Relation:0x1047ef978> 

activerecord (3.0.3) lib/active_record/relation.rb:371:in `method_missing' 
app/views/products/show.html.haml:18:in `_app_views_products_show_html_haml___1131941434_2185376080_0' 

我认为它是与所创建的新关系，但林不知道如何着手，轨道导向仍然表明这种方法是可以的。

//编辑后由弗朗索瓦修改建议：是

类定义如下：

class Product < ActiveRecord::Base 
    has_many :product_related_products 
    has_many :related_products, :through => :product_related_products 
end 

class ProductRelatedProduct < ActiveRecord::Base 
    belongs_to :product 
    belongs_to :related_product, :class_name => "Product" 

    scope :with_attribute, lambda {|attr| where(attr, true)} 

end 


@product.related_products.with_attribute(:alternative) raises: 

NoMethodError Exception: undefined method `with_attribute' for #<Class:0x108fbd8b8> 

Answer 1

定义在相关类的范围：

class RelatedProduct < ActiveRecord::Base 

    scope :visible, where(:hidden, false) 

    %w(alternative complement bigger_pack higher_quantity lower_quality).each do |attribute| 
    scope attribute, where(attribute, true) 
    end 

end 

@product.related_products.visible.bigger_pack 

另外，建立一个单一的方法，期望您正在搜索的属性：

class RelatedProduct < ActiveRecord::Base 
    scope :with_attribute, lambda {|attr| where(attr, true)} 
end 

@product.related_products.visible.with_attribute(:bigger_pack)