Moped: get id after inserting

Question

When I use mongo-ruby-driver and I insert new document it returns generated '_id':

db = MongoClient.new('127.0.0.1', '27017').db('ruby-mongo-examples')
id = db['test'].insert({name: 'example'})

# BSON::ObjectId('54f88b01ab8bae12b2000001')

I'm trying to get the '_id' of a document after doing an insertion using Moped:

db = Moped::Session.new(['127.0.0.1:27017'])
db.use('ruby-mongo-examples')
id = db['coll'].insert({name: 'example'})

# {"connectionId"=>15, "n"=>0, "syncMillis"=>0, "writtenTo"=>nil, "err"=>nil, "ok"=>1.0}

How I get the id using Moped?

Update:

I also try use safe mode but it doesn't work:

db = Moped::Session.new(['127.0.0.1:27017'])
db.use('ruby-mongo-examples')

db.with(safe: true) do |safe|
  id = safe['coll'].insert({name: 'example'})

  # {"connectionId"=>5, "n"=>0, "syncMillis"=>0, "writtenTo"=>nil, "err"=>nil, "ok"=>1.0}
end

Fortin

You can get it in the response if you do a safe insert or generate it before the insert like document = { _id: Moped::BSON::ObjectId.new, name: "example" } id = document[:_id] – Sept

I found this issue: github.com/mongoid/moped/issues/129. It seems that the only way is generte id with BSON::ObjectId.new and use it. Thanks @chridam. – Fortin

I think @hamster_ham's answer is more appropriate than mine, your call to accept it. – Sept

Answer 1

From this issue:

It would be nice, but unfortunately Mongo doesn't give us anything back when inserting (since it's fire and forget), and when in safe mode it still doesn't give the id back if it generated it on the server. So there really isn't any possible way for us to do this unless it was a core feature in MongoDB.

Your best bet would be to generate the id before inserting the document:

document = { _id: Moped::BSON::ObjectId.new, name: "example" } 
id = document[:_id]

Sept

hamster_ham's answer is more consistent with how you would expect mongo to work i.e. insert document get id back in result. – Johny

@ChrisMcCauley I do agree, OP's call to switch the accepted answer though. – Sept

Well said chridam - respect ! – Johny

It is a good solution if you don't want to be waiting for mongo. – Brittani

Answer 2

After inserting/saving, the returned object will have a property inserted_id which is a BSON::ObjectId:

# I'm using insert_one
result = safe['coll'].insert_one({name: 'example'})   
result.methods.sort        # see list of methods/properties
result.inserted_id
result.inserted_id.to_s    # convert to string

Metrical

worked for me without the "safe['coll']", just coll.insert_one(...) – Deegan