ZCCADCDEDB567ABAE643E15DCF0974E503Z 使用默认选定字段填充虚拟

Question

I have this virtual in a mongoose schema:

PostSchema.virtual("author", {
    ref: "User",
    localField: "userId",
    foreignField: "_id",
    justOne : true,
});

and when i call .find() , I can populate it like this:

PostSchema.find(...).populate("author", "displayName username avatar")

As you can see I only selected some fields to populate into author , this works fine and gives me the result that I want.

But is it possible to set the default selected fields when creating a virtual on my Schema? Probably something like this:

PostSchema.virtual("author", {
    ref: "User",
    localField: "userId",
    foreignField: "_id",
    justOne : true,
    fields: "displayName username avatar"
});

so I don't have to put selected fields on the 2nd parameter every time I call populate.

PostSchema.find(...).populate("author")
// `author` still will only contains displayName, username, and avatar, not the whole fields from User schema

Answer 1

You can define a function on your User schema, which returns only specific fields you want:

UserSchema.method('getAuthorFields', function () {
  return {
    displayName: this.displayName,
    username: this.username,
    avatar: this.avatar
  }
})

And then you can define mongoose post middleware of your find in your post schema which will be triggered after data is fetch from the db:

PostSchema.post('init', function () {
    this.author = this.author.getAuthorFields();
});