如何在猫鼬js中嵌套相同的架构

Question

I'm trying to nest schemas using mongoose js, specifically the same schema, to create a tree-like structure. In this configuration, a document can only have 1 parent, but the same document can be parent to more than one child. Here's how I approached it initially:

var mongoose = require('mongoose'),
Schema = mongoose.Schema,
ObjectId = Schema.ObjectId;

var mySchema = new Schema({
    _id: {
        type: ObjectId,
        required: true
    },
    parent: {
        _id: { 
            type: ObjectId, 
            ref: 'myModel'
        },
        required: true
    }
});

var myModel = mongoose.model('myModel', mySchema);

module.exports = {
    myModel: mongoose.model('myModel', myModel)
};

However, when I run this, I get the

A JavaScript error occurred in the main process Uncaught Exception: TypeError: Undefined type "undefined" at "file.required" Did you try nesting Schemas? You can only nest using refs or arrays.

I must be approaching this wrong. How do you nest the same schema using mongoose js?

Answer 1

The warning already show you "You can only nest using refs or arrays.". This is a mongoose design.

But what you can do is:

var MySchema = new mongoose.Schema({
    objectId: String,
    parent: {
        type: mongoose.Schema.ObjectId,
        ref: 'MySchema'
    },
})

This will use a schema inside a schema, then you can use a "pre save" to update the data of your parent. Or you can use a array of refs and keep with only 1 element.

What a do is export the schemas and not the models, so you can nest it. like this:

module.exports = MySchema;

Then I have some appModel to set the models of my collection of schemas, like this (app_model.js):

if(mongoose.modelNames().indexOf('mySchema') < 0) mongoose.model('mySchema', mySchema);