ruby-on-rails - 如何创建多态关系的种子

Question

我有三个对象:

class Picture < ActiveRecord::Base
  belongs_to :imageable, :polymorphic => true
end

class Employee < ActiveRecord::Base
  has_many :pictures, :as => :imageable  
end

class Product < ActiveRecord::Base
  has_many :pictures, :as => :imageable
end

我应该如何创建测试种子数据，将图像与种子员工和种子产品相关联？

Answer 1

to associate an image with both a seed employee and seed product

这需要一个多对多关系(has_and_belongs_to_many 或has_many :through):

#app/models/product.rb
class Product < ActiveRecord::Base
  has_many :images, as: :imageable
  has_many :pictures, through: :images
end

#app/models/employee.rb
class Employee < ActiveRecord::Base
  has_many :images, as: :imageable
  has_many :pictures, through: :images
end

#app/models/image.rb
class Image < ActiveRecord::Base
  belongs_to :imageable, polymorphic: true
  belongs_to :picture
end

#app/models/picture.rb
class Picture < ActiveRecord::Base
  has_many :images
end

这将允许您使用:

#db/seed.rb
@employee = Employee.find_or_create_by x: "y"
@picture  = @employee.pictures.find_or_create_by file: x

@product = Product.find_or_create_by x: "y"
@product.pictures << @picture

ActiveRecord, has_many :through, and Polymorphic Associations

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因为您正在使用多态 关系，所以您将无法使用has_and_belongs_to_many。

上面将在join 表上设置多态性；每张 Picture 都是“裸”的(没有“创作者”)。需要一些黑客来定义图像的原始创建者。