Push an object into a nested array in MongoDB - mongodb

Question

I've got a head-scratcher here that I'd like to share with you all.
So here's the model:
_id: ObjectId()
name: String,
columns: [
{
name: String,
_id: ObjectId()
tasks: [
{
title: String,
description: String,
status: String,
_id: ObjectId()
subtasks: [
{
title: String,
isCompleted: Boolean,
},
],
},
],
},
],
});
and the query:
exports.createSubtask = (req, res) => {
if (!req.body) {
res.status(400).send({ message: "Task name can not be empty!" });
return;
}
const board = req.params.board;
const column = req.params.column;
const task = req.params.task;
Board.findOneAndUpdate(
{
_id: board,
"columns._id": column,
"columns.tasks._id": task,
},
{
$push: {
"columns.$.tasks.$.subtasks": req.body,
},
}
)
.then((data) => {
if (!data) {
res.status(404).send({
message: `Cannot update Task with id=${task}. Maybe task was not found!`,
});
} else res.send({ message: "Task was updated successfully." });
})
.catch((err) => {
res.status(500).send({
message: "Error updating Task with id=" + task,
});
});
};
I'm trying to push an object into the subtasks array with $push, but Postman is throwing an error.
Any ideas as to what I'm doing wrong? Appreciate the help.
Golden Ratio
However, I was able to successfully push an object into the tasks array with the following query:
exports.createTask = (req, res) => {
if (!req.body) {
res.status(400).send({ message: "Task name can not be empty!" });
return;
}
const board = req.params.board;
const column = req.params.column;
Board.findOneAndUpdate(
{
_id: board,
"columns._id": column,
},
{
$push: {
"columns.$.tasks": req.body,
},
}
)
.then((data) => {
if (!data) {
res.status(404).send({
message: `Cannot update Column with id=${column}. Maybe column was not found!`,
});
} else res.send({ message: "Column was updated successfully." });
})
.catch((err) => {
res.status(500).send({
message: "Error updating Column with id=" + column,
});
});
};

Answer 1

It is not possible to use multiple positional $ for the nested array as mention in docs:
The positional $ operator cannot be used for queries which traverse more than one array, such as queries that traverse arrays nested within other arrays, because the replacement for the $ placeholder is a single value
You should work with the positional filtered operator $[<identifier>].
Board.findOneAndUpdate(
{
_id: board,
"columns._id": column,
"columns.tasks._id": task,
},
{
$push: {
"columns.$.tasks.$[task].subtasks": req.body,
},
},
{
arrayFilters: [
{ "task._id": task }
]
}
)
.then(...);
Note: Ensure that the passed in task is ObjectId type.

Answer 2

Credit to Yong Shun Yong for the help. Through trial and error, I solved the problem with the following code
Board.findOneAndUpdate(
{
_id: board,
"columns._id": column,
},
{
$push: {
"columns.$.tasks.$[].subtasks": req.body,
},
},
{
arrayFilters: [{ "task._id": task }],
}
)