singleObj = await Objects.findByIdAndUpdate({ _id: req.body.id, }, { $inc: { 'total_obj': -1, 'total_stuff': 1 }, }, { new: true })
The user clicks a button and the value of 'total_obj' gets decreased by one. The value doesn't have to be less than 0. I have tried to do this:
singleObj = await Objects.findByIdAndUpdate(
{ _id: req.body.id, "total_obj": { "$lt": 0 } },
{ "$set": { "total_obj": 0 } }
);
But this messes up every time I load the page and I have the values set to 0. I also added on the definition on the schema:
total_obj: {
type: Number,
required: true,
min: 0
},
I assume you meant that you don't want your value to be lesser than 0.
You would need to use $gt operator and while you used $inc properly in the first findByIdAndUpdate you didn't use it in the second one.
Also, we are not looking only for id so we should use findOneAndUpdate instead.
singleObj = await Objects.findOneAndUpdate(
{ _id: req.body.id, "total_obj": { "$gt": 0 } },
{ $inc: { "total_obj": -1 } }
);
Try to fetch the Objects instance first and update the value only if > 0:
const singleObj = await Objects.findById(req.body.id)
if (!singleObj) // Error, obj not found
if (singleObj.total_obj > 0) {
singleObj.total_obj = singleObj.total_obj-1
await singleObj.save()
} else {
// `total_obj` is already zero
}