#objectid

original source : https://stackoverflow.com/questions/2819242/core-data-objectid-changes-constantly

core data에서 자체 만들어지는 NSManagedObjectID는 수시로 바뀔수 있음으로 이를 특정 데이터를 접근하기 위한 고유 id로 사용해서는 안된다.

The NSManagedObjectID is not guaranteed to be consistent. It can change based on a number of factors including data migration and other factors. If you are using this as a unique identifier for your objects, stop.

The only time you want to use the NSManagedObjectID is when you need to pass references between threads. Other than that situation you should not rely upon it for anything.

Converting a hexstring to ObjectId for MongoDB in Javascript

How to convert a string value to ObjectID

Sometimes, the ObjectID of your MongoDB document is delivered as a 24 character hexstring. You can’t just compare this hexstring to an ObjectID, because the comparison will fail.

The solution is as follows:

var mongoose = require('mongoose' ); var hexstring = '58666c89d4bc6622ed5373dc'; // convert it to ObjectID var ObjIDtype =…

MongoDB : Post 3.1 : BSON ‘ObjectID’

ObjectId’s have the following characteristics:

Each document in a collection in MongoDB has an unique ‘_id’.If you look closely Objectid’s are different in all the documents.So each time when you create a document an ‘_id’ will be generated.This id field acts as a primary key,so if by any chance  _id field is not present  in documents, MongoDB uses ObjectIds as the default value for the…

I would just like to take a moment and celebrate writing my first POST api endpoint that creates a Mongoose object and saves it to the Mongodb. I held off celebrating after I wrote a GET, but now it's proper time. The hardest part about writing the POST was figuring out why I kept being unable to retrieve the new object's id. Searching surfaced what seemed to be simply accessing the "._id" or ".id" attribute of the new object instance. However, I kept getting errors of the form:

return this._id.toString(); ^ TypeError: Cannot call method 'toString' of undefined at model. (node_modules/mongoose/lib/mongoose/schema.js:45:23) at VirtualType.applyGetters (node_modules/mongoose/lib/mongoose/virtualtype.js:52:25) at model.Document.get (node_modules/mongoose/lib/mongoose/document.js:376:18) at model.Object.defineProperty.get [as id] (node_modules/mongoose/lib/mongoose/document.js:609:41) at Promise. (server.js:127:35) at Promise. (node_modules/mongoose/lib/mongoose/promise.js:120:8) at Promise.EventEmitter.emit (events.js:95:17) at Promise.emit (node_modules/mongoose/lib/mongoose/promise.js:57:38) at Promise.complete (node_modules/mongoose/lib/mongoose/promise.js:68:20) at complete (node_modules/mongoose/lib/mongoose/model.js:73:13)

or simply an "undefined" value when logging the .id or ._id property. It turns out the model was defined incorrectly because the '_id' property was specified as a string, like this:

contestData = { _id: String, words: [String], time_limit: Number, genre: [String], status: String, entries: [postData] };

Once the _id property was removed from the model definition, the _id property was accessible as expected.

Gardez le cap !

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Extraindo a parte incremental de um ObjectId do MongoDb

No MongoDB todos os documentos são automaticamente criados com um _id. Normalmente esse _id é um O…

If you ever have to deal with serializing/deserializing Mongo ObjectIds using Jackson, then you'll want to give this blog post a read: http://simplapi.wordpress.com/2013/06/18/handling-mongodb-objectid-threw-jerseyjackson/

In short - out of the box, Jackson will serialize an ObjectId into its constituent parts but will be unable to put that back together due to ObjectId limitations. The solution: Write a customer serializer that turns an ObjectId into a String. ObjectId's know how to handle Strings as input on the deserialization side. 

To query documents by ObjectID, you can't just pass in a string, you need to send in PHP's Object/Type MongoID

public function action_getstuff() { $mongodb= \Mongo_Db::instance('default'); $userID1 = '4f98c2f6f26c618f21000002'; $userID2 = '4f976a38f26c619121000002'; $result = $mongodb->where_in('_id', array($userID1, $userID2))->get('Users'); if($result) { echo "got Results with userID strings"; } $result = null; $mongoID1 = new MongoID($userID1); $mongoID2 = new MongoID($userID2); $result = $mongodb->where_in('_id', array($mongoID1, $mongoID2))->get('Users'); if($result) { echo "got Results with MongoID objects"; } }