Mongoose Change Order of Array of Objects not working

Question

There is a person Michael who has favoriteFruits = [ { name: 'Apple'}, {name: 'Banana'} ]

What I want to do is changing its order

[ { name: 'Apple'}, {name: 'Banana'} ]

to

[ { name: 'Banana'}, {name: 'Apple'} ]

So I did :

Members.findOne({ name: 'Michael' }, function(err, member){
    member.favoriteFruits = [ {name: 'Banana'}, {name: 'Apple'} ]

    member.save(function (err, result){

        // result is favoriteFruits = [ { name: 'Banana'}, {name: 'Apple'} ]
        // result is correct, but real db's order not changed.

    })
})

Even result's order of favoriteFruits is correct, but the order of db is not changed. The order is not changed.

I guess MongoDB assume this job is useless task so it doesn't do anything. How can I update order?

Apart from the result issue, why you are not using findOneAndUpdate instead of two separate queries? — Ved
– Ved, Commented Oct 1, 2018 at 11:30
@Ved Sometimes I use, sometimes not. Especially when I have to handle something with queried data. — ton1
– ton1, Commented Oct 1, 2018 at 11:32
@AnkitAgarwal Perhaps should I add another key value pair such as [{ name: 'Banana', index: 0, { name: 'Apple', index: 1 }] and order by index...? I hope there will be more simple way.... — ton1
– ton1, Commented Oct 1, 2018 at 11:41

nijm · Accepted Answer · 2018-10-01 13:41:15Z

0

Most likely Mongoose is not noticing the difference between the arrays. You can tell Mongoose that the field has actually been modified by using the Document.prototype.markModified() method.

For your example:

Members.findOne({ name: 'Michael' }, function(err, member) {
    member.favoriteFruits = [{ name: 'Banana' }, { name: 'Apple' }];
    member.markModified('favoriteFruits');

    member.save(function (err, result) {

    });
});

answered Oct 1, 2018 at 13:41

nijm

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