Mongodb how to move specific object from array to another array?

Question

Suppose I have the following collection:

{  
  "_id":ObjectId("562e7c594c12942f08fe4192"),
  "first":[  
    {  
      "shape":"square",
      "color":"blue"
    },
    {  
      "shape":"circle",
      "color":"red"
    }
  ],
  "second": []
}

What I want to do is, first find a specific object inside the first array and move that to second field

db.collection.findOneAndUpdate({_id: ObjectId("562e7c594c12942f08fe4192")}, {$pull: {first: {color: "red"}}, $push: {// that specific object to second array}})

dnickless · Accepted Answer · 2018-10-22 20:20:50Z

2

This cannot be done in a single operation. You can do this instead, though:

MyModel.findOne({ _id: ObjectId("562e7c594c12942f08fe4192"), "first.color": "red" }, 'first.$', function (err, doc) {
    MyModel.findByIdAndUpdate(ObjectId("562e7c594c12942f08fe4192"), {
        $pull: { first: { color: "red" } },
        $push: { second: doc.first[0] }
    }, function (err, docs) {  })
});

answered Oct 22, 2018 at 20:20

dnickless

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Comments

Jack · Accepted Answer · 2018-10-22 12:10:24Z

Try this using cursors.

db.getCollection('test')
    .find({_id: ObjectId("562e7c594c12942f08fe4192")})
    .forEach(function(doc) {
        doc.second = doc.first.filter(function(x) { return x.color === "blue"});
        doc.first = doc.first.filter(function(x) { return x.color !== "blue" });
        db.getCollection('test').save(doc)
    }
)

Replace "blue" with your chosen item.

This will however work for your example but will remove any previous items in second.

If you just want to append it this should work.

db.getCollection('test')
    .find({_id: ObjectId("562e7c594c12942f08fe4192")})
    .forEach(function(doc) {
         doc.second = doc.second.concat((doc.first.filter((x) => x.color === "green")));
         doc.first = doc.first.filter(function(x) { return x.color !== "green" });
         db.getCollection('test').save(doc)
      }
)

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