铁轨4中的相互关系

2 回答

• 3

  您正在寻找的是has_and_belongs_to_many关系，但是对于同一个表，有点像Many-to-many relationship with the same model in rails?详细描述的那样 . 但是，由于您希望关系是双向的（"my friends are all also friends with me"），因此您有两种选择：

  • 使用单个连接表，每个连接表链接两个user_id，但为每个友谊插入两行 .

  # no need for extra columns on User
  class User < ActiveRecord::Base
    has_many :friendships
    has_many :friends, through: :friendships
  end
  
  # t.belongs_to :user; t.belongs_to :friend
  class Friendship < ActiveRecord::Base
    belongs_to :user
    belongs_to :friend, class_name: "User"
  end
  
  u1 = User.create!
  u2 = User.create!
  u3 = User.create!
  
  # make users 1 and 2 friends
  u1.friendships.create(friend: u2)
  u2.friendships.create(friend: u1)        
  
  # make users 2 and 3 friends
  u2.friendships.create(friend: u3)
  u3.friendships.create(friend: u2)        
  
  # and now, u1.friends returns [u1],
  # u2.friends returns [u1, u3] and
  # u3.friends returns [u2].
  

  • 使用单个记录，但hackery找到你的朋友：

  # no need for extra columns on User
  class User < ActiveRecord::Base
    has_many :friendships_as_a, class_name: "Friendship", foreign_key: :user_a_id
    has_many :friendships_as_b, class_name: "Friendship", foreign_key: :user_b_id
  
    def friends
      User.where(id: friendships_as_a.pluck(:user_b_id) +          friendships_as_b.pluck(:user_a_id))
    end
  end
  
  # t.belongs_to :user_a; t.belongs_to :user_b
  class Friendship < ActiveRecord::Base
    belongs_to :user_a, class_name: "User"
    belongs_to :user_b, class_name: "User"
  end
  

  这不是最干净的方法，但我认为你会发现在设置这样的时候（使用非规范化表）并没有真正特别干净的方法 . 选项1是一个更安全的赌注 . 您还可以通过自动生成每个友谊的镜像条目，使用SQL视图来达到中间位置 .

  编辑：API中的迁移和使用

  根据下面的OP评论，要完全使用选项1，这是您需要做的：

  rails g migration CreateFriendships
  

  将该文件编辑为：

  class CreateFriendships < ActiveRecord::Migration
    create_table :friendships do |t|
      t.belongs_to :user
      t.belongs_to :friend
      t.timestamps
    end
  end
  

  创建友谊模型：

  class Friendship < ActiveRecord::Base
    belongs_to :user
    belongs_to :friend, class_name: "User"
  end
  

  然后在您的用户模型上：

  class User < ActiveRecord::Base
    # ...
  
    has_many :friendships
    has_many :friends, through: :friendships, class_name: 'User'
  
    # ...
  end
  

  在您的API中，请说一个新的FriendshipsController：

  class FriendshipsController < ApplicationController
    def create
      friend = User.find(params[:friend_id])
  
      User.transaction do # ensure both steps happen, or neither happen
        Friendship.create!(user: current_user, friend: friend)
        Friendship.create!(user: friend, friend: current_user)
      end
    end
  end
  

  你的路线是什么样的（在 config/routes.rb ）：

  resource :friendships, only: [:create]
  

  并且请求看起来像：

  POST /friendships?friend_id=42
  

  然后，只要您想查找用户是谁的朋友，您就可以参考 current_user.friends .

  回复于 2024-04-28T22:13:08+08:00
• 1

  你用has_many :through：

  #app/models/user.rb
  class User < ActiveRecord::Base
    has_many :friendships
    has_many :friends, through: :friendships, -> { where(status: "accepted") }
  end
  
  #app/models/friendship.rb
  class Friendship < ActiveRecord::Base
    belongs_to :user
    belongs_to :friend, class_name: "User"
  
    enum status: [:pending, :accepted]
    validates :user, uniqueness: { scope: :friend, message: "You can only add a friend once" }
  
    def decline
      self.destroy
    end
  
    def accept
      self.update status: "approved"
    end
  end
  

  以上是self-referential join，允许以下内容：

  @user   = User.find params[:id]
  @friend = User.find params[:friend_id]
  
  @user.friends << @friend
  

  这将为用户添加新的 friendship ，其默认 status 设置为 pending . 设置了 @user.friends 关联，以便仅通过呼叫显示 accepted 个朋友 .

  因此，您将能够执行以下操作：

  #config/routes.rb
  resources :users do
    resources :friendships, only: [:index, :destroy, :update], path_names: { destroy: "remove", update: "accept" }
  end
  
  #app/controllers/Frienships_controller.rb
  class FriendshipsController < ApplicationController
    def index
      @user       = User.find params[:user_id]
      @friendship = @user.friendships
    end
  
    def update
      @user       = User.find params[:user_id]
      @friendship = @user.friendships.find params[:id]
      @friendship.accept
    end
  
    def destroy
      @user       = User.find params[:user_id]
      @friendship = @user.friendships.find params[:id]
      @friendship.decline
    end
  end
  
  #app/views/friendships/index.html.erb
  <%= @friendships.pending.each do |friendship| %>
    <%= link_to "Accept", user_friendships_path(user, friendship), method: :put %>
    <%= link_to "Decline", user_friendships_path(user, friendship), method: :delete %>
  <% end %>
  

  回复于 2024-04-28T22:13:08+08:00