猫鼬：填充没有任何 ObjectId 的猫鼬

Question

我有 2 个模式，如图所示

const gameSchema = new mongoose.Schema({
    title: String,
    rating: { type: Number, min: 0, max: 100 },
    genres: { type: Array, ref: 'Genres' }
})
const GenreSchema = new mongoose.Schema({
    id: { type: Number },
    name: String,
    description: String
})
mongoose.model('Games', gameSchema)
mongoose.model('Genres', GenreSchema)

现在一个端点 /api/games returns 一组游戏结果，其中 genres 属性包含 id 数组，例如。 "genres": [4, 7, 19]

如何在没有任何 ObjectId 的情况下填充 genres？我试过使用普通的 ref 方法，但它说

{"stringValue":"\"4\"","kind":"ObjectId","value":4,"path":"_id","reason":{},"message":"Cast to ObjectId failed for value \"4\" at path \"_id\" for model \"Genres\"","name":"CastError"}

我想将它指向 id 而不是 _id

Answer 1

可以使用Virtuals的概念。这是怎么回事：

修改您的架构文件如下：

//---------------------------------------------------
const gameSchema = new mongoose.Schema({
  title: String,
  rating: { type: Number, min: 0, max: 100 },
  genres: [Number],//here you have an array of id of type Number as yours, no ref
});
const GenreSchema = new mongoose.Schema({
  id: { type: Number },
  name: String,
  description: String,
});

gameSchema.virtual("games", {
  ref: "Genres",//this is the model to populate
  localField: "id",//the field used to make the populate, it is the field that must match on the aimed  Genres model <- here is the trick you want!!!  
  foreignField: "genres",//the field to populate on Games model
  justOne: false,
});

 gameSchema.set("toObject", { virtuals: true });//if you are planning to use say console.log
 gameSchema.set("toJSON", { virtuals: true });//if you are planning to use say res.json

mongoose.model("Games", gameSchema);
mongoose.model("Genres", GenreSchema);
//-------------------------------------------------

在您要填充的文件中，将其放在声明部分：

//-----------------------------------------------------
const Games = mongoose.model("Games", gameSchema);
//---------------------------------------------------

最后但同样重要的是，您要填充的位置：

//----------------------------------------------
Games.find({})
  .populate("games")
  .exec(function (error, games) {
   //with games you can use things like game.field1, it is actually an JSON object! Print out games and see the fieds for your self, select one and call it using the dot notation! 
    console.log(games);
  });
//---------------------------------------------

我已经针对我遇到的问题测试了此解决方案，只是根据您的需要进行了修改，请让我知道它是否适用于您的问题；如果没有，我们可以一起弄清楚如何使我的解决方案适合您的需求。

一些初步参考

Populate a mongoose model with a field that isn't an id

猫鼬：填充没有任何 ObjectId 的猫鼬

mongoose: populate in mongoose which doesn't have any ObjectId

mongoose

mongodb

mongoose-populate