多态has_and_belongs_to_many [英] Polymorphic has_and_belongs_to_many

问题描述

情况:

图中显示我们具有用户，曲目，列表等...，并且可以标记所有这些模型并将其用作过滤器.

我想做的是:

使用has_and_belongs_to_many使标签具有其他对象，并且其他对象也可以具有其他标签.

Use has_and_belongs_to_many that enable to a tag to have other objects, and that other objects also can have other tags.

因此，要启用属于一种以上对象(用户，轨道或轨道列表)的标签，我们需要使用多态关系.

So for enable a tag that belongs to more than one kind of object (users or tracks or tracklists), we need to use polymorphic relations.

这是我目前的代码:

class CreateTags < ActiveRecord::Migration[5.2]
  def change
    create_table :tags do |t|
      t.string :name
      t.references :taggable, polymorphic: true, index: true
      t.timestamps
    end
    create_table :assemblies_parts, id: false do |t|
      t.belongs_to :assembly, index: true
      t.belongs_to :part, index: true
    end
  end
end

标记模型

class Tag < ApplicationRecord
  has_and_belongs_to_many :taggable, polymorphic: true
end

用户模型

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  has_and_belongs_to_many :tags, as: :taggable
  has_one :top_list
  has_many :tracks, through: :top_list

end

轨道模型

class Track < ApplicationRecord
  has_and_belongs_to_many :tags, as: :taggable
  belongs_to :top_list
end

推荐答案

您可以使用has_many关联:

标记模型

class Tag < ApplicationRecord
  has_many :relation
end

关系模型

class Relation < ApplicationRecord
  belongs_to :tag
  belongs_to :taggable, polymorphic: true
end

用户模型

class User < ApplicationRecord
  has_many :relations, as: :taggable
  has_many :tags, through: :relations

  has_one :top_list
  has_many :tracks, through: :top_list
end

跟踪模型

class Track < ApplicationRecord
  has_many :relations, as: :taggable
  has_many :tags, through: :relations

  belongs_to :top_list
end

标签迁移

class CreateTags < ActiveRecord::Migration[5.2]
  def change
    create_table :tags do |t|
      t.string :name
      t.timestamps
    end
    create_table :relations, id: false do |t|
      t.references :tags, index: true
      t.references :taggable, polymorphic: true, index: true
    end
  end
end

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