在 Rails 中关联 Post、Comment、User 和 Vote 模型的有效方法是什么? [英] What's an efficient way of associating Post, Comment, User and Vote models in Rails?

问题描述

现在，我有三个模型 Post、Comment 和 User(使用 Devise)，关联如下:

Right now, I have three models Post, Comment and User (using Devise) associated as follows:

post.rb:

class Post < ActiveRecord::Base
  attr_accessible :title, :content, :total_votes

  validates :title,   :presence => true,
                      :length   => { :maximum => 30 },
                      :uniqueness => true
  validates :content, :presence => true,
                      :uniqueness => true

  belongs_to :user
  has_many :comments, :dependent => :destroy
end

comment.rb:

class Comment < ActiveRecord::Base
  attr_accessible :content, :user_id

  belongs_to :post, :counter_cache => true
  belongs_to :user
end

user.rb:

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :token_authenticatable, :encryptable, :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable,
         :omniauthable
  # Setup accessible (or protected) attributes for your model
  attr_accessible :email, :password, :password_confirmation, :remember_me, :username

  validates_presence_of :username
  has_many :posts, :dependent => :destroy
  has_many :comments, :dependent => :destroy

  def self.find_for_facebook_oauth(access_token, signed_in_resource=nil)
    data = access_token.extra.raw_info
    if user = User.where(:email => data.email).first
      user
    else # Create a user with a stub password. 
      User.create!(:email => data.email, :password => Devise.friendly_token[0,20]) 
    end
  end
end

我想添加第四个名为 Vote 的模型，条件如下:

I want to add a fourth model called Vote with the following conditions:

1. 帖子和评论都可以投票(向上和向下)并显示总数.
2. 每个帖子都会有很多票(上下)并显示总数/总和.
3. 每个评论都会有很多票
4. 每次投票时都应存储用户的 ID，以便我可以限制每个用户投一票并显示投票用户的 ID/姓名(不确定将其存储在哪里)

1. Both posts and comments can be voted (up and down) and show the total/sum.
2. Each post will have many votes (up and down) and show the total/sum.
3. Each comment will have many votes
4. The ID of the user should be stored each time he or she votes so I can restrict one vote per user and show the ID/name of the users who voted (not sure where to store it)

现在，我不确定这是否是使用多态关联和/或计数器缓存的好时机.

Now, I'm not sure if this is a good occasion to use polymorphic associations and/or counter cache.

将这些帖子、评论、用户和投票模型关联起来的有效方法是什么?(如果可能，我想看看迁移的样子)

What's an efficient way of associating these Post, Comment, User and Voting models? (If possible, I would like to see how the migration would look like)

推荐答案

这是一个完美的教科书示例，说明了 多态关联会很有用.

This is a perfect textbook example of where a polymorphic association would be useful.

您的 votes 表迁移如下所示:

Your votes table migration would look like this:

create_table :votes do |t|
  t.references :votable, :polymorphic => true
  t.references :user
  t.integer :polarity
  t.integer :total
end

这将创建一个具有此架构的表:

This would create a table with this schema:

id INTEGER
votable_id INTEGER
votable_type VARCHAR
user_id INTEGER
polarity INTEGER
total INTEGER

这里，user_id 将是投票者，polarity 将是1"表示赞成或-1"表示反对(这让您只需将极性相加即可获得赞成票和反对票以取消)，votable_type 将包含投票的内容(Post 或 Comment)，votable_id 将包含投票对象的 id，total 将保留投票总和的运行总数(为了效率).

Here, user_id would be the person who cast the vote, polarity would be either '1' for an upvote or '-1' for a downvote (this lets you just sum the polarities to get upvotes and downvotes to cancel), votable_type would contain what the vote is for (Post or Comment), votable_id would contain the id of the thing the vote is for, and total would keep a running total of the vote sum (for efficiency).

那么您的模型将如下所示:

Then your models would look like this:

class Vote < ActiveRecord::Base
    belongs_to :votable, :polymorphic => true
    belongs_to :user

    before_create :update_total

    protected

    def update_total
        self.total ||= 0
        self.total += self.polarity
    end
end

class Post < ActiveRecord::Base
    has_many :votes, :as => :votable
end

class Comment < ActiveRecord::Base
    has_many :votes, :as => :votable
end

class User < ActiveRecord::Base
    has_many :votes
end

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