What is the managed object context?

A managed object context represents a single object space, or scratch pad, in a Core Data application. A managed object context is an instance of NSManagedObjectContext . It’s the object you use to create and fetch managed objects, and to manage undo and redo operations.

Can we create multiple managed object context?

You should not access your NSManagedObjectContext on multiple threads. The NSManagedObjectContext created in your AppDelegate should only be accessed on main thread. It implies, you should create a NSManagedObjectContext for each thread you create.

What is managed object in Core Data?

A managed object model is a set of objects that together form a blueprint describing the managed objects you use in your application. A model allows Core Data to map from records in a persistent store to managed objects that you use in your application.

What is single managed object?

A single managed object instance exists in one and only one context, but multiple copies of an object can exist in different contexts. Therefore, an object is unique to a particular context.

Is Core Data a Threadsafe?

Core Data is designed to work in a multithreaded environment. However, not every object under the Core Data framework is thread safe. To use Core Data in a multithreaded environment, ensure that: Managed object contexts are bound to the thread (queue) that they are associated with upon initialization.

Is NSManagedObject thread safe?

You should never pass a NSManagedObject instance from one thread to another. The NSManagedObject class is not thread-safe. The Core Data framework provides a solution to pass managed objects from one thread to another, the NSManagedObjectID class.

What is the difference between GCD and NSOperationQueue in iOS?

GCD is a low-level C-based API that enables very simple use of a task-based concurrency model. NSOperation and NSOperationQueue are Objective-C classes that do a similar thing. NSOperation was introduced first, but as of 10.5 and iOS 2, NSOperationQueue and friends are internally implemented using GCD .

Is NSSet thread safe?

The documentation on NSSet objectEnumeration says: When this method is used with mutable subclasses of NSSet, your code shouldn’t modify the set during enumeration. If you intend to modify the set, use the allObjects method to create a “snapshot” of the set’s members.

How many managed object model can a persistent store coordinator have?

one Persistent Store Coordinator
Q: How many Managed Object Model, a Persistent Store Coordinator can have? We can have only one Persistent Store Coordinator for each model.

What is managed object context in core data?

A managed object context is an in-memory scratchpad for working with your managed objects. Most apps need just a single managed object context. The default configuration in most Core Data apps is a single managed object context associated with the main queue.

How does a managed object remain in memory?

Changes to managed objects remain in memory in the associated context until Core Data saves that context to one or more persistent stores. A single managed object instance exists in one and only one context, but multiple copies of an object can exist in different contexts. Therefore, an object is unique to a particular context.

When does a child managed object context save its changes?

When a child managed object context saves its changes, it pushes them to the parent managed object context. In other words, when a child managed object context saves its changes, the persistent store coordinator is unaware of the save operation.

When to use nsmanagedobjectcontext in core data?

In situations such as store migration, Core Data will create instances of NSManagedObjectContext for its own use. Under these circumstances, you cannot rely on any features of your custom subclass.