用户在使用 Sequelize 之前是否喜欢过该帖子

Question

当前，当用户喜欢某个帖子时，该喜欢的记录会使用 userId 和 postId 添加到我的 Likes 表中。

现在，当用户查看帖子时，我想确定他们之前是否喜欢该帖子。我知道要这样做，我需要在我调用发布信息时在我的 get 请求中确定这一点。

当我调用帖子信息时，我需要检查 Likes 表以获取当前用户的 userId 和当前帖子的 postId 的记录。如果存在，那么我需要返回一个名为 isLiked 的参数并将其设置为 true，如果它不存在则 isLiked=false。

这是我的帖子模型：

id: {
  type: Sequelize.INTEGER,
  primaryKey: true,
  autoIncrement: true,
},
title: {
  type: Sequelize.STRING,

},
userId: {
  type: Sequelize.INTEGER,
},
likesCount:{
  type:Sequelize.INTEGER,
  defaultValue:0,
  validate: {
            min: 0,
        }
},

这是我的点赞模型：

id: {
allowNull: false,
autoIncrement: true,
primaryKey: true,
type: Sequelize.INTEGER,
 },
 PostId: {
type: Sequelize.INTEGER,
references: {
  model: "Post",
  key: "id",
},
 },
 userId: {
type: Sequelize.INTEGER,
references: {
  model: "User",
  key: "id",
},
 },

这是我的用户模型：

id: {
  type: Sequelize.INTEGER,
  primaryKey: true,
  autoIncrement: true,
},
name: {
  type: Sequelize.STRING,
 },

这是我的联想：

User.hasMany(Post, { foreignKey: "userId" });
Post.belongsTo(User, { foreignKey: "userId" });

Post.hasMany(Likes, { foreignKey: "PostId", targetKey: "id" });
Likes.belongsTo(Post, { foreignKey: "PostId", targetKey: "id" });

User.hasMany(Likes, { foreignKey: "userId", targetKey: "id" });
Likes.belongsTo(User, { foreignKey: "userId", targetKey: "id" });

更新

我一直在研究并发现，因为我正在使用 JWT 中间件来签署我的用户令牌，并且我目前正在检查当前用户是否在 likes 表中有任何记录，我尝试了以下但有人可以告诉我是否这种做法正确吗？

 router.get("/", async (req, res) => {
    const posts = await Post.findAll({
   order: [["createdAt", "DESC"]],
   include: [
  { model: Post_Image, attributes: ["id", "images"] },
  { model: Likes, attributes: ["id", "PostId", "userId"] },
  ],
  });

 if (!posts) return res.status(404).send();

 const baseUrl = config.get("assetsBaseUrl");

 const plainPosts = posts.map((x) => x.get({ plain: true }));
 const resultPosts = [];
  for (const post of plainPosts) {

 let isLiked = false;
 let like = await Likes.findOne({
where: {
[Op.and]: [{ PostId: post.id) }, { userId: 
req.user.id }],

  },
 });

if (like) isLiked = true;

const { Post_Images, ...postAttributes } = post;
const IMAGES = Post_Images.map((postImage) => ({
  url: `${baseUrl}${postImage.images}_full.jpg`,
  thumbnailUrl: `${baseUrl}${postImage.images}_thumb.jpg`,
}));
resultPosts.push({ ...postAttributes, images: IMAGES, isLiked 
});
}

res.send( resultPosts );

 });

Answer 1

您不需要指定所有字段，除非您想覆盖某些内容，否则 Sequelize 可以为您生成大部分列。

const User = sequelize.define(
  'user',
  {
    name: {
      type: Sequelize.STRING,
    },
  },
  { /* options */ }
);

const Post = sequelize.define(
  'post',
  {
    title: {
      type: Sequelize.STRING,
    },
  },
  { /* options */ }
);

// the join table so you can reference it, but doesn't need any columns including primary key (unless you want to a "super join")
const Likes = sequelize.define(
  'likes',
  {}, // no columns here
  { /* options */ }
);

创建模型之间的关联将自动创建大部分外键字段。在Likes 关系上使用through 关键字使其成为多对多。

// Users can have many Posts
User.hasMany(Post);

// Posts belong to one User
Post.belongsTo(User);

// Users can like more than one Post through the `likes` join table
User.hasMany(Post, { as: 'likes', through: 'likes' });

// Posts can be liked by more than one User through the `likes` join table
Post.hasMany(User, { as: 'likes', through: 'likes' });

您不需要存储喜欢的数量，因为您可以通过连接表对其进行汇总。

// Get the 'likes' count for a Post, instead of saving it on the post
const posts = await Post.findAll({
  attributes: {
    include: [
      [sequelize.fn('COUNT', sequelize.col('likes.userId')), 'likesCount'],
    ],
  },
  include: [
    {
      model: User,
      as: 'likes',
      though: 'likes',
      attributes: [],
      required: false,
    },
  ],
});

// `posts` will be an array of Post instances that have a likesCount property
posts.forEach((post) => {
  console.log(`The post ${post.title} has ${post.likesCount} likes.`);
});

对于单个（或多个）帖子，您可以通过帖子获得喜欢它的用户列表（或使用Like 模型及其关系）。

// Get the user 'likes' for a Post
const post = await Post.findByPk(postId, {
  include: [
    {
      model: User,
      as: 'likes',
      though: 'likes',
      required: false,
    },
  ],
});

post.likes.forEach((like) => {
  console.log(`The user ${like.name} has liked the post ${post.title}.`);
});

Answer 2

您无需再次请求Like，所有帖子的赞都在您手边：

for (const post of plainPosts) {
 // check if we have any like among posts' likes that is made by a certain user
 const isLiked = post.Likes.some(x => x.userId === req.user.id);
 const { Post_Images, ...postAttributes } = post;
 ...