Question

团队，寻找Rails 4协会非常具体（新手）情况的帮助。我们有3个型号：

class Brand < ActiveRecord::Base
 has_many :lines, dependent: :destroy
 has_many :products, through: :lines, dependent: :destroy
end

class Line < ActiveRecord::Base
 belongs_to :brand
 has_and_belongs_to_many :products
end

class Product < ActiveRecord::Base
 has_and_belongs_to_many :lines
 has_many :brands, through: :lines
end

尝试在特定Products（或Brand）下检查Line时，此配置效果很好，反之亦然：不同的Brands（或Lines）可用对于特定的Product。但是，当涉及到删除/销毁时，存在一个问题。我们收到此Rspec错误：

ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection:
Cannot modify association 'Brand#products' because the source reflection 
class 'Product' is associated to 'Line' via :has_and_belongs_to_many.

我们对此异常进行了研究，检查了Rails API，没有运气，发现的示例显示了不同的模型配置。这种方法缺少什么？

感谢你们的帮助！

Answer 1

在我看来，它应该是这样的：

class Brand < ActiveRecord::Base
 has_many :lines, dependent: :destroy
 has_many :products, through: :lines, dependent: :destroy
end

class Line < ActiveRecord::Base
 belongs_to :brand
 has_and_belongs_to_many :products
end

class Product < ActiveRecord::Base
 belongs_to :brand, through: :line
 has_and_belongs_to_many :lines
end

在迁移中：

create_table :brands , force: true do |t|
  t.string :name
  ...
  t.timestamps null: false    
end

create_table :lines , force: true do |t|
  t.string :name
  t.belongs_to :brand
  ...
  t.timestamps null: false    
end

create_table :products , force: true do |t|
  t.string :name
  ...
  t.timestamps null: false    
end

create_table :line_products, force: true, id: false do |t|
  t.belongs_to :line, index: true
  t.belongs_to :product, index: true
end

我希望它会有所帮助。

Rails 4 HABTM has_many：through

1 个答案: