Mongoose findOneAndUpdate - update one field using another [duplicate]

Question

Consider this schema:

var UserSchema = new Schema({
    ...
    user_id: {type:String},
    previous_selection: {type:String},
    current_selection: {type:String}
});

I need to write a function, which will update the value of previous_selection with the value of current_selection for the given user_id.

Is there any way of doing this with findOneAndUpdate?

Something like -

MyModel.findOneAndUpdate(
        { user_id: id }, 
        { $set: {"previous_selection": current_selection }},
        {}, 
        callback
);

Or is there a better way to implement this? Will I have to do a find() and then update?

you cannot update a field with another one in single update you have to call a find method to accomplish this — wrangler
– wrangler, Commented Nov 7, 2017 at 12:07

Srikar Jammi · Accepted Answer · 2017-11-07 12:20:46Z

4

As per your concern you can do this to update entire collection.

db.MyModel.find({}).snapshot().forEach(
function (elem) {
    db.MyModel.update(
        {
            _id: elem._id
        },
        {
            $set: {
                "previous_selection": elem.current_selection
            }
        }
    );
});

else you can find by id and can update with respective current_selection.

answered Nov 7, 2017 at 12:20

Srikar Jammi

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3 Comments

Ramsing Nadeem Over a year ago

What does .snapshot() do?

Srikar Jammi Over a year ago

It simply prevents returning the doc more than once.

Ramsing Nadeem Over a year ago

Nice; but returning the same doc more than once, or duplicates?

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