My Api Code Retrieves An Empty Data Array From Mongodb While The Code Works Well On Mongodb Playground

My mongodb database includes a collection of users and each user has an array of shops and each shop has an array of products. Here is a simplified version of my collection structu

Solution 1:

Turns out the casting of the ObjectId seemed to be the issue. We need to use mongoose.Types.ObjectId

The API code will looks like this

getProductByProductId: function (productId) {
returnnew Promise((resolve, reject) => {
  User.aggregate([
  {
  $match: {
    "shops.products._id": mongoose.Types.ObjectId(productId)
  }
  },
  {
    "$unwind": "$shops"
  },
  {
    "$unwind": "$shops.products"
  },
  {
    $match: {
    "shops.products._id": mongoose.Types.ObjectId(productId)
  }
  },
  {
  $project: {
  "_id": "$shops.products._id",
  "title": "$shops.products.title"
  }
}
])
.then(products => {
resolve(products)
}).catch(err => {
reject(err);
});
});
}