How to populate nested fields in schema mongodb - arrays

Question

I have a summary schema with a structure like this
{
sender: {
type: mongoose.Schema.Types.ObjectId,
ref: "User",
required: true,
},
summary: {
type: String,
},
sent: {
type: Date,
default: Date.now,
},
}
);
then a convo schema:
NOTE: summary in this schema is an array of objectId, convo returns an array of objects after fetching, sender is in each of the objects gotten after populating the summary field
{
lastMessage: {
type: mongoose.Schema.Types.ObjectId,
ref: "messages",
},
members: {
type: [mongoose.Schema.Types.ObjectId],
ref: "User",
required: true,
},
summary: {
type: [mongoose.Schema.Types.ObjectId],
ref: "summary",
},
gigDetails: {
type: mongoose.Schema.Types.ObjectId,
ref: "Gig",
},
}
I want to populate the sender field in the summary array in the convo schema when fetching it, in addition to the already populated summary field.
How can I do this?

Answer 1

You can do it like this:
ConvoModel.find(filter).populate([{ path: 'summary', populate: { path: 'sender' } }])

Answer 2

// Fetch the convo documents
const convos = await Convo.find()
.populate("summary")
.exec();
// Iterate through the convos array
for (let i = 0; i < convos.length; i++) {
// Iterate through the summary array and populate the sender field in each element
const summaryPromises = convos[i].summary.map(async summary => {
return await summary.populate('sender').execPopulate();
});
// Wait for all promises to resolve
await Promise.all(summaryPromises);
}