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ViewsMongoose - How to increment a field by value of another field
I am new to mongoose ODM. I am trying to increment a value by the value of another field. Following is what I have tried :
const deletedCartItem = await Cart.findOneAndUpdate(
{ sessionId: req.session.sessionId, "productInfo.productId": product_id },
{
$inc: {
checkoutAmount: "$productInfo.totalAmount"//totalAmount is a nested field here.
},
$pull: {
productInfo: { productId: product_id },
},
},
{ new: true, useFindAndModify: false }
);
The schema of my collection looks like :
const cartSchema = mongoose.Schema({
sessionId: {
type: String,
unique: true,
},
checkoutAmount: {
type: Number,
},
orderStatus: {
type: String,
default: "INCART"
},
productInfo: [
{
productId: {
type: String,
required: true,
unique: true,
},
quantity: {
type: Number,
required: true,
},
price: {
type: Number,
},
totalAmount: {
type: Number,
}
}
],
});
The error I am getting is - 
Am I missing something here ? Thanks in advance !
·
Santiago Trujillo
1 answers
Answer question0
Update can't allow to use internal field's value into another fields, you have to go with update with aggregation pipeline starting from MongoDB 4.2,
$reduceto iterate look ofproductInfoand check condition ifproductIdmatch then return itstotalAmount,$addto increment thecheckoutAmountwith returnedtotalAmountfrom above$reduceoperation$filterto iterate loop ofproductInfoand filter the elements that do not have matchingproductId
const deletedCartItem = await Cart.findOneAndUpdate(
{ sessionId: req.session.sessionId, "productInfo.productId": product_id },
[{
$set: {
checkoutAmount: {
$add: [
"$checkoutAmount",
{
$reduce: {
input: "$productInfo",
initialValue: 0,
in: {
$cond: [
{ $eq: ["$$this.productId", product_id] },
"$$this.totalAmount",
"$$value"
]
}
}
}
]
},
productInfo: {
$filter: {
input: "$productInfo",
cond: { $ne: ["$$this.productId", product_id] }
}
}
}
}],
{ new: true, useFindAndModify: false }
);
·
Santiago Trujillo
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