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Question

Trying to update a document in MongoDB using the official mongo driver,go.mongodb.org/mongo-driver/mongo

this is my struct that I want to update

type Activity struct {
    Timestamp    time.Time          `bson:"timestamp,omitempty"`
    Type         string             `bson:"type,omitempty"`
}

type Member struct {
    ID           primitive.ObjectID `bson:"_id,omitempty"`
    Name         string             `bson:"name,omitempty"`
    Activities []Activity           `bson:"activities ,omitempty"`
}

this is the code for updating document

filter := bson.M{"_id": m.ID}
update := bson.M{
    "$set": bson.M{
        "name":        m.Name,
    },
    "$each": bson.M{"activities": m.Activities },
}

res, err := coll.UpdateOne(ctx, filter, update)

the name gets updated but nothing happens with the activities

what am I doing wrong? should I use ReplaceOne instead?

Answer 1

the name gets updated but nothing happens with the activities

This is because $each array update operator is designed to be used with $addToSet (append unique) or $push(append).

For example, if you would like to update the array with no duplicate activities the set:

update := bson.M{
    "$set": bson.M{
        "name": obj.Name,
    },
    "$addToSet": bson.M{"activities": bson.M{"$each": obj.Activities }},
}
cursor, err := collection.UpdateOne(context.Background(), filter, update )