Mongo adding an object to original object - mongodb-query

Question

I am not sure if I am asking the correct question but I assume this is just a basic mongodb question.
I currently have this:
{
"_id" : ObjectId("57af98d4d71c4efff5304335"),
"fullname" : "test",
"username" : "test",
"email" : "test#gmail.com",
"password" : "$2a$10$Wl29i6FemBrnOKq/ZErSguxlfvqoayZQkaEDirkmDl5O3GDEQjOV2"
}
and I would like to add an exercise object like this:
{
"_id" : ObjectId("57af98d4d71c4efff5304335"),
"fullname" : "test",
"username" : "test",
"email" : "test#gmail.com",
"password" : "$2a$10$Wl29i6FemBrnOKq/ZErSguxlfvqoayZQkaEDirkmDl5O3GDEQjOV2",
"exercises": {
"benchpress",
"rows",
"curls",
}
I am just unsure how to create exercises with the object without using $push which just opens up an array. I don't want an array, I want an object.
Any help would be greatly appreciated it.

Answer 1

An object is a key-value pair. In your representation of the second document, you have a nested document exercises as a key and its value as an object containing only strings. Don't you see something strange there? An object without keys?
It should probably be an array of strings. Note that an array is indeed an object where the key is the numeric index starting from 0 and the value is the string in that position.
(You have an additional comma and a missing curly-brace. Lets fix that.)
This is the document we wish to see after updating the document.
{
"_id" : ObjectId("57af98d4d71c4efff5304335"),
"fullname" : "test",
"username" : "test",
"email" : "test#gmail.com",
"password" : "$2a$10$Wl29i6FemBrnOKq/ZErSguxlfvqoayZQkaEDirkmDl5O3GDEQjOV2",
"exercises": [
"benchpress",
"rows",
"curls"
]
}
Now, back to your question. How can we update the existing document with the exercises document? Its pretty simple. Mongodb has a 'update' method which exactly does that. Since we don't want to replace the entire document and just add additional fields, we should use $set to update specific fields. Fire up the mongo shell and switch to your database using use db-name. Then execute the following command. I assume you have an existing document with id ObjectId("57af98d4d71c4efff5304335"). Note that ObjectId is a BSON datatype.
db.scratch.update({ "_id" : ObjectId("57af98d4d71c4efff5304335") }, { $set: {"exercises": ["benchpress", "rows", "curls"] } })
This will update the document as
{
"_id" : ObjectId("57af98d4d71c4efff5304335"),
"fullname" : "test",
"username" : "test",
"email" : "test#gmail.com",
"password" : "$2a$10$Wl29i6FemBrnOKq/ZErSguxlfvqoayZQkaEDirkmDl5O3GDEQjOV2",
"exercises" : [
"benchpress",
"rows",
"curls"
]
}
Here scratch refers to the collection name. The update method takes 3 parameters.
Query to find the document to update
The Update parameter(document to update). You can either replace the whole document or just specific parts of the document(using $set).
An optional object which can tell Mongodb to insert the record if the document doesn't exist(upsert) or update multiple documents that match the criteria(multiple).
EXTRA
Warning: If you execute the following in the mongo shell,
db.scratch.update({ "_id" : ObjectId("57af98d4d71c4efff5304335") }, {"exercises": ["benchpress", "rows", "curls"] })
the entire document would be replaced except the _id field. So, the record would be something like this:
{
"_id" : ObjectId("57af98d4d71c4efff5304335"),
"exercises" : [
"benchpress",
"rows",
"curls"
]
}
You should only do this when you are aware of the consequence.
Hope this helps.
For more, see https://docs.mongodb.com/manual/reference/method/db.collection.update/