What are best practices for Core Data in Swift?

// Example: Setting up a Core Data Model
import CoreData

class PersistenceController {
    static let shared = PersistenceController()

    let container: NSPersistentContainer

    init(inMemory: Bool = false) {
        container = NSPersistentContainer(name: "ModelName")

        if inMemory {
            container.persistentStoreDescriptions.first?.url = URL(fileURLWithPath: "/dev/null")
        }
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
    }
}

// Fetching Data
func fetchEntities() {
    let fetchRequest: NSFetchRequest = EntityName.fetchRequest()
    
    do {
        let results = try container.viewContext.fetch(fetchRequest)
        // Handle results
    } catch {
        // Handle error
    }
}