Has_many不同模型在Rails中的关联

Question

I have a few different models which I would like to add multiple images to.

I have an image model with belongs_to associations set up to the different owning models (each of these owning models has has_many :images defined).

I would like to know what's the appropriate migration I should create in order to add an image_ids column to each of owning models.

I assume something like this...

rails g migration AddImagesToBusinesses images businesses image_ids:integer

However, I'm confused as I believe that you can only make one association this way and it would need to be completed by adding a column to the images table to identify the id of the model it belongs to (here there are a few different models).

Thank you for your help.

Answer 1

I think you need Polymorphic associations. See documentaions here.

Answer 2

As you concern about relationship of image to other model. You should try polymorphic associations like this.

Generate the Image model:

class CreateImages < ActiveRecord::Migration
  def change
    create_table :images do |t|
      t.string :file_id
      t.boolean :featured
      t.references :imageable, polymorphic: true, index: true
      t.timestamps null: false
    end
  end
end

Update the Image model:

class Image < ActiveRecord::Base
  attachment :file
  belongs_to :imageable, polymorphic: true
end

Add association to other models like this

class Model < ActiveRecord::Base
  has_many :images, as: :imageable, dependent: :destroy
  accepts_attachments_for :images, attachment: :file
end

For more details you Ruby on Rails Guide .