What is predicate in Core Data?

Core Data fetch requests can use predicates in SwiftUI just like they can with UIKit, all by providing a predicate property to your @FetchRequest property wrapper. Once that’s done, you can create a fetch request for one of your entities, passing in one or more sort descriptors and a predicate.

How do you write NSPredicate?

In Swift, constructors skip the “blahWith…” part and just use the class name as a function and then go straight to the arguments, so [NSPredicate predicateWithFormat: …] would become NSPredicate(format: …) . (For another example, [NSArray arrayWithObject: …] would become NSArray(object: …) .

What is NSPredicate?

A definition of logical conditions used to constrain a search either for a fetch or for in-memory filtering.

What is fetched property in Core Data?

Fetched Properties in Core Data are properties that return an array value from a predicate. A fetched property predicate is a Core Data query that evaluates to an array of results.

What is NSFetchRequest?

An instance of NSFetchRequest collects the criteria needed to select and optionally to sort a group of managed objects held in a persistent store. A fetch request must contain an entity description (an instance of NSEntityDescription ) or an entity name that specifies which entity to search.

What are relationships in Core Data?

A relationship specifies the entity, or the parent entity, of the objects at the destination. This entity can be the same as the entity at the source (a reflexive relationship). Relationships do not have to reference a single entity type.

How can I recover my Core Data?

Retrieve Data

  1. Prepare the request of type NSFetchRequest for the entity (User in our example)
  2. if required use predicate for filter data.
  3. Fetch the result from context in the form of array of [NSManagedObject]
  4. Iterate through an array to get value for the specific key.

Is Core Data thread safe?

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.

What is NSDictionary?

The NSDictionary class declares the programmatic interface to objects that manage immutable associations of keys and values. Each entry consists of one object that represents the key and a second object that is that key’s value. Within a dictionary, the keys are unique.