Rails has_many通过过滤的关联

Question

我想为两个单独但非常相似的关联使用一个连接模型。以下是我有：

两个主要型号有：包装，尺寸

Pacakges有多种尺寸，但有皱纹。尺寸需要分配为顶部或底部的尺寸。我的包目前协会有：

has_many :package_sizes 
has_many :sizes, :through => :package_sizes 
has_many :bottoms_sizes, :through => :package_sizes, :scope => {:package_sizes => {:bodylocation => "B"}}, :source => :size 
has_many :tops_sizes, :through => :package_sizes, :scope => {:package_sizes => {:bodylocation => "T"}}, :source => :size 

包装尺寸与联接模型：size_id | package_id | bodylocation：字符串

我有一个失败的测试，以验证它是否工作：

@p = Package.new 
@size1 = Size.first 
@p.tops_sizes << @size1 
@p.save 
@p.reload 
@p.tops_sizes.should include(@size1) 

这应该正常工作，但由于某种原因，bodylocation场不会被自动设置。

任何想法？

Answer 1

尝试为此创建两个单独的直通关联。

has_many :bottom_package_sizes, :class_name => 'PackageSize', :conditions => {:bodylocation => 'B'} 
has_many :top_package_sizes, :class_name => 'PackageSize', :conditions => {:bodylocation => 'T'} 
has_many :bottom_sizes, :through => :bottom_package_sizes 
has_many :top_sizes, :through => :top_package_sizes 

Answer 2

有（恕我直言）较好地解决了这个在回答：Scope with join on :has_many :through association。

本质上，它会是这样的：

has_many :package_sizes 
has_many :sizes, :through => :package_sizes do 
    def tops 
    where("package_sizes.bodylocation = 'T'") 
    end 
    def bottoms 
    where("package_sizes.bodylocation = 'B'") 
    end 
end 

然后，您可以查询他们喜欢：

@p.sizes.tops