在Sequelize中像Web应用程序一样在Twitter中进行多对多自我参考

问题描述

我正在尝试构建一个博客网络应用程序，作为一种特别了解ORM和Sequelize的技能.我很容易地在帖子和评论与用户和帖子之间建立关系.那里没有问题.当我尝试将用户链接为关注者并将用户链接到用户时，恐怖开始了.我也希望能够跟随自己.

I'm trying to build a blog web-application as an excercise to understand ORM and Sequelize in particular. I managed quite easily to form relations between posts and comments and users and posts. No problems there. The horror begins when I try to link users to users as followers and users to users as followeds. I also want it to be possible to follow yourself.

我尝试过这样的事情:

  const User = sequelize.define('user', {
    firstName: {
      type: Sequelize.STRING
    },
    lastName: {
      type: Sequelize.STRING
    },
    email: {
      type: Sequelize.STRING
    },
    password: {
      type: Sequelize.STRING
    },
    activated: {
      type: Sequelize.BOOLEAN
    }
  })
User.belongsToMany(User, {as: "Follower", foreignKey: "FollowerId", through: "Follower_Followeds"})
User.belongsToMany(User, {as: "Followed", foreignKey: "FollowedId", through: "Follower_Followeds"})

并设置关系:

app.post("/followhandler", function(req, res) {
    let userId = req.session.userId
    let followId = req.body.followId

    User.findById(userId)
    .then( currentUser => {
        User.findById(followId)
        .then( follows => {
            currentUser.addUser(follows)
        })
    })
    .catch(e => console.log(e)) 
})

但是Follower_Followeds表将不会更新.我还尝试通过创建单独的表并手动添加关系来跳过Sequelize的许多实现:

But the Follower_Followeds table will simply not get updated.I've also tried to skip the many to many implementation of Sequelize by creating a separate table and adding the relations manually:

const FollowerFollowed = sequelize.define('followerFollowed', {
  followedId: {
    type: Sequelize.INTEGER
  },

  followerId: {
    type: Sequelize.INTEGER
  }  
})

//define Users
  const User = sequelize.define('user', {
    firstName: {
      type: Sequelize.STRING
    },
    lastName: {
      type: Sequelize.STRING
    },
    email: {
      type: Sequelize.STRING
    },
    password: {
      type: Sequelize.STRING
    },
    activated: {
      type: Sequelize.BOOLEAN
    }
  })

处理程序:

app.post("/followhandler", function(req, res) {
    let userId = req.session.userId
    let followId = req.body.followId

    FollowerFollowed.create( {
        followerId: userId,
        followedId: followId
    })
    .then( rel => console.log(rel))
    .catch(e => console.log(e)) 
})

但是在这种情况下，我收到以下错误消息:

But I'm getting the following error in this case:

推荐答案

创建M:M关联时，请使用 as:'Follower'和 as:'Followed'属性.它影响您​​可以在用户之间添加/设置/删除关联的方式.现在，将关注的用户添加到其他用户的方法称为 addFollowed ，其使用方式与您完全相同.

When you create the M:M association you use as: 'Follower' and as: 'Followed' attributes. It influences the way you can add/set/delete associations between users. Method to add followed user to other user is now called addFollowed and would be used in exactly the same way you did it.

User.findById(userId).then( currentUser => {
    User.findById(followId).then( follows => {
        currentUser.addFollowed(follows); // notice the difference here
    });
});

如果要向指定用户添加关注者，则会发生相同的情况-那么您将使用 addFollower 方法.

The same occurs if you want to add follower to given user - then you would use addFollower method.

此外，在第二种解决方案中，您在创建关联模型时犯了一个错误.在 User 模型中，您已通过外键 FollowerId 和 FollowedId 定义了关联，但是在 FollowerFolloweds 定义中创建了 followerId 和 followedId ，因此这两个不匹配-您需要保持名称一致.

Moreover, in your second solution you have made a mistake while creating the associating Model. In the User model you have defined associations via foreign keys FollowerId and FollowedId, however in the FollowerFolloweds definition you have created followerId and followedId, so those two do not match each other - you need to keep the names consistent.

编辑

根据 belongsToMany 关系中的文档， as 属性应命名为复数，因此在您的情况下，应将这些命名为:'Followers'和如:'Followeds'(第二个似乎有点奇怪).Sequelize将这些值本身单数化，但是您可以使用对象自己定义为:{单数:'Follower'，复数:'Followers'}

According to the documentation in the belongsToMany relation, the as attribute should be named as plural, so in your case you should name those as: 'Followers' and as: 'Followeds' (the second one seems a little strange). Sequelize singularizes those values itself, however you can define it by yourself using object as: { singular: 'Follower', plural: 'Followers' }

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