Polymorphic Table VS Join Table

example.md

has_many :through Association

A Post can have many Tags and a Tag can belong to many Posts. A has_many :through association may seem like a good approach, but what if a new model is introduced that also needs to have many Tags?

clas Post < ApplicationRecord
  has_many :post_tags
  has_many :tags, through: :post_tags
end

clas Tag < ApplicationRecord
  has_many :post_tags
  has_many :posts, through: :post_tags
end

clas PostTag < ApplicationRecord
  belongs_to :post
  belongs_to :tag
end

Polymorphic Association

Would a Polymorphic associations be more flexible? This would allow for additional models to be tagged later.

clas Post < ApplicationRecord
  has_many :tags, as: :taggable
end

clas Tag < ApplicationRecord
  belongs_to :taggable, polymorphic: true
end