Check out example codes for "Core Data Quickest way to delete all instances of an entity swift". It will help you in understanding the concepts better.

Code Example 1

public func clearDatabase() {
    guard let url = persistentContainer.persistentStoreDescriptions.first?.url else { return }

    let persistentStoreCoordinator = persistentContainer.persistentStoreCoordinator

     do {
         try persistentStoreCoordinator.destroyPersistentStore(at:url, ofType: NSSQLiteStoreType, options: nil)
         try persistentStoreCoordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: nil)
    } catch let error {
         print("Attempted to clear persistent store: " + error.localizedDescription)
        }
    }
}

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