猫鼬：以没有任何ObjectId的猫鼬填充

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返回游戏的结果数组，其中genres属性包含ID数组，例如。 "genres": [4, 7, 19]

如何在没有任何genres的情况下填充ObjectId？我尝试使用普通的ref方法，但是它说

{"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"}

我想将其指向id，而不是_id

Answer 1

您可以使用Virtuals的概念。这是怎么回事：

如下修改您的架构文件：

//---------------------------------------------------
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);
//-------------------------------------------------

在您要填充的文件上，将其放在声明部分：

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

最后但并非最不重要的，要填充的位置：

//----------------------------------------------
Games.find({})
  .populate("games")
  .exec(function (error, games) {
    console.log(games);
  });
//---------------------------------------------

我已经针对已解决的问题测试了该解决方案，请对其进行修改以满足您的需求，请告诉我它是否可以解决您的问题；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。

一些初始参考文献

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