How to check if ObjectId exist in collection

[Sergey Di]

Hi,
Could you please help, how to check if ObjectId exist in collection?
From mongo console I do it:
> db.collection.find({_id: ObjectId("5bb216a8475fe42644993a40")}, {_id: 1}).limit(1);
How to do the same using MongoKitten?

[Joannis Orlandos]

In MongoKitten 4:

let document = try collection.findOne("_id" == <my-objectId>)

In MongoKitten 5:

collection.findOne("_id" == <my-objectId>).then { document in 
    ...
}

[Sergey Di]

@Joannis <my-objectId> must be String value of objectId or some objectId value?

[Joannis Orlandos]

An ObjectId value in your case. try ObjectId("5bb216a8475fe42644993a40") would produce a static one.

Realistically an _id key in MongoDB can contain any value you wish to put there including string, integer, document, double and many others, as long as it's unique. So a user might have it's email address under the _id key, but you don't apparantly :)

[Sergey Di]

let mongoClient = try MongoKitten.Database("mongodb://\(username):\(password)@\(ipAddress)/\(database)")
let myCollection = mongoClient[collection]
let oid = try ObjectId("5bb216a8475fe42644993a41")
let document = try myCollection.findOne("_id" ==  oid)

document is nil in any case (ObjectId exist and not exist)

[Joannis Orlandos]

Are you reading through the right collection/database? Try creating a server instance first using the string and then explicitly selecting the database using the subscript.

let client = try MongoKitten.Server("mongodb://\(username):\(password)@\(ipAddress)")
let myCollection = client[database][collection]

[Sergey Di]

It was error on my side. Thank you. Everything works perfect :)

[Sergey Di]

Also, how to get the same result using find method, because findOne takes much more resources than find method?

[Joannis Orlandos]

It does not, findOne does not take any more resources since they're the same command.

for document in collection.find("_id" == oid, limitedTo: 1) {
  print(document) // only executes once
}

The above will be the same performance and everything, but will have more (complex) code.

[Joannis Orlandos]

When I mean findOne is the same thing as find, I really mean the same thing

[Sergey Di]

Thank you :)