get virtual attribute for each nested object in an array of objects?

Question

So I know how to get a single virtual attribute, as stated in the Mongoose docs:

PersonSchema
 .virtual('name.full')
 .get(function () {
   return this.name.first + ' ' + this.name.last;
});

But what if my schema is:

var PersonSchema = new Schema({
    name: {
      first: String
    , last: String
    },

    arrayAttr: [{
      attr1: String,
      attr2: String
    }]
})

And I want to add a virtual attribute for each nested object in arrayAttr:

PersonSchema.virtual('arrayAttr.full').get(function(){
    return attr1+'.'+attr2;
});

Lemme know if I missed something here.

Answer 1

Sure, you can define an extra schema, but mongoose is already doing this for you.

It is stored at

PersonSchema.path('arrayAttr').schema

So you can set a virtual by adding it to this schema

PersonSchema.path('arrayAttr').schema.virtual('full').get(function() {
  return this.attr1 + '.' + this.attr2
})

Answer 2

If you want a calculated value from all the array elements here's an example:

const schema = new Schema({
    name:         String,
    points: [{
        p:      { type: Number, required: true },
        reason: { type: String, required: true },
        date:   { type: Date,   default: Date.now }
    }]
});

schema.virtual('totalPoints').get(function () {
    let total = 0;
    this.points.forEach(function(e) {
        total += e.p;
    });
    return total;
});

User.create({
    name:   'a',
    points: [{ p: 1, reason: 'good person' }]
})

User.findOne().then(function(u) {
    console.log(u.toJSON({virtuals: true}));
});

Returns to:

{ _id: 596b727fd4249421ba4de474,
  __v: 0,
  points:
   [ { p: 1,
       reason: 'good person',
       _id: 596b727fd4249421ba4de475,
       date: 2017-07-16T14:04:47.634Z,
       id: '596b727fd4249421ba4de475' } ],
  totalPoints: 1,
  id: '596b727fd4249421ba4de474' }