Generic Data Base Manager for Core Data

DBManager.swift

import UIKit
import CoreData

class DBManager {
    private static var managedObjectContext: NSManagedObjectContext {
        return (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    }
    
    class func create<E>(proccess: (_ object: E) -> Void) -> Bool {
        do {
            proccess(NSEntityDescription.insertNewObject(forEntityName: "\(E.self)", into: managedObjectContext) as! E)

            try managedObjectContext.save()
            
            return true
        }
        catch let error {
            fatalError(error.localizedDescription)
        }
        
        return false
    }
    
    class func read<E>(proccess: ((_ fetchRequest: NSFetchRequest<NSFetchRequestResult>) -> Void)?) -> [E] {
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "\(E.self)")
        
        proccess?(fetchRequest)
        
        do {
            return try managedObjectContext.fetch(fetchRequest) as! [E]
        }
        catch let error {
            fatalError(error.localizedDescription)
        }
    }
    
    class func update<E>(proccess: ((_ fetchRequest: NSFetchRequest<NSFetchRequestResult>) -> Void)?, update: (_ objects: [E]) -> Void) -> Bool {
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "\(E.self)")
        
        proccess?(fetchRequest)
        
        do {
            update(try managedObjectContext.fetch(fetchRequest) as! [E])
            try managedObjectContext.save()
            
            return true
        }
        catch let error {
            fatalError(error.localizedDescription)
        }
        
        return false
    }
    
    class func delete<E>(proccess: ((_ fetchRequest: NSFetchRequest<NSFetchRequestResult>) -> Void)?, deletedObjects: ((_ objects: [E]) -> Void)?) -> Bool {
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "\(E.self)")
        
        do {
            let objects = try managedObjectContext.fetch(fetchRequest) as! [E]

            deletedObjects?(objects)
            
            for object in objects {
                managedObjectContext.delete(object as! NSManagedObject)
            }
            
            try managedObjectContext.save()
            
            return true
        }
        catch let error {
            fatalError(error.localizedDescription)
        }
        
        return false
    }
    
}