Difference Between NSManagedObject, NSManagedObjectContext and NSManagedObjectModel

Question

What is difference between these three classes [NSManagedObject , NSManagedObjectContext , NSManagedObjectModel ] of core-data and how can we describe in easiest Way?

score 52 · Accepted Answer · answered May 11 '12 at 12:49

52

In database terms:

NSManagedObject = a row
NSManagedObjectContext = a transaction
NSManagedObjectModel = a schema

Of course, Core Data isn't a database.

answered May 11 '12 at 12:49

Stephen Darlington

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Thanks. Its Short but Great answer. This can be the simplest way we can understand core data if we already worked on sql. Please provide some more details or any article link where such type of description and we can better know in terms of SQL. – iMash May 11 '12 at 13:04
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A context is more like a client or connection than like a transaction. – paulmelnikow May 17 '12 at 02:57
A `NSManagedObjectContext` class, wraps a mutable layer around an `NSManagedObjectModel` instance. – Abhishek Bedi Feb 05 '13 at 09:51
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@DeepakThakur sqlite isn't the only backend for Core Data. You can also use binary, XML, in-memory or even write your own (just saw one using [Realm](https://github.com/eure/RealmIncrementalStore/tree/master/RealmIncrementalStore)). Having said that, what they mean is, if you use it in the same way that you would use a SQL database, you're likely to have problems. And that's true, regardless of the underlying technology. – Stephen Darlington Feb 26 '16 at 10:06

Abhishek Bedi · Answer 2 · 2016-01-10T06:09:18.613

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From CoreData programming guide :

You can think of a managed object context as an intelligent scratch pad. When you fetch objects from a persistent store, you bring temporary copies onto the scratch pad where they form an object graph (or a collection of object graphs). You can then modify those objects however you like. Unless you actually save those changes, however, the persistent store remains unaltered.

edited Jan 10 '16 at 06:09

answered Feb 05 '13 at 10:50

Abhishek Bedi

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- Good, and what about NSManagedObject? – AsifHabib Jan 06 '21 at 11:48

score 2 · Answer 3 · answered Dec 06 '18 at 04:33

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NSManagedObjects represent data stored in the database. You can think of them as model objects.

NSManagedObjectContext allows you to insert, save, and retrieve (using NSFetchRequest) NSManagedObjects from the database.”

answered Dec 06 '18 at 04:33

Farooque Azam

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Jpellat · Answer 4 · 2012-05-11T12:58:24.843

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An NSManagedObject herits from object, and adds the methods necessary to be managed by core data.

The context is where the objects that are being managed by core data are saved, that happens when you take an object from the dataBase or you create to save to it

The object model describes a coredata schema for the persistent store

edited May 11 '12 at 12:58

answered May 11 '12 at 12:47

Jpellat