mongoose subdocument field.id giving undefined

Question

in this code i need to take batch_results using its genarated id like described in mongoose documents

const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const config = require('../config/config');



// Result schema
const ResultsSchema = new Schema({
    subject_id: {
        type: mongoose.SchemaTypes.ObjectId,
        required: false
    },
    marks: {
        type: [String], // when needed to store absent as well
        required: false
    }
});

// Batch Schema
const BatchSchema = new Schema({
    student_base_no: {
        type: mongoose.SchemaTypes.ObjectId,
        required: false,
    },
    results: [ResultsSchema]
});

// Marks schema
const MarksSchema = new Schema({

    date: {
        type: Date,
        default: Date.now,
        required: true
    },
    year: {
        type: String,
        default: (new Date).getFullYear(),
        required: true
    },
    batch: {
        type: String,
        required: true
    },
    batch_results: [BatchSchema]

});



const Marks = module.exports = mongoose.model('marks', MarksSchema, 'marks');

using this code i tried getting the output ,

var a = Marks.batch_results.id(id)

but it keeps saying Cannot read property 'id' of undefined

I tried a lot but no good :( please help me guys ...

Answer 1

You need to change batch and marks schema :

const BatchSchema = new Schema({
    student_base_no: {
        type: mongoose.SchemaTypes.ObjectId,
        required: false,
    },
    results:{
         type: Schema.Types.ObjectId,
          ref: 'results' 
       }
})