Nice functions for dealing with CoreData

NSManagedObjectExtension.swift

//
//  NSManagedObject.swift
//
//  Created by Marcos Santos on 8/30/18.
//  Copyright © 2018 Marcos Santos 2018. All rights reserved.
//

import Foundation
import CoreData

extension NSManagedObject {
    
    convenience init(saving: Bool = true) throws {
        let context = try DataManager.getContext()
        if let entity = NSEntityDescription.entity(forEntityName: String(describing: type(of: self)), in: context) {
            self.init(entity: entity, insertInto: saving ? context : nil)
        } else {
            throw Errors.wrongEntityName
        }
    }
    
    public func insertIntoContext() throws {
        if !self.isInserted {
            let context = try DataManager.getContext()
            context.insert(self)
        }
    }
    
    public func delete() throws {
        let context = try DataManager.getContext()
        context.delete(self)
        
        do {
            try context.save()
        } catch {
            throw Errors.cantDeleteObject
        }
    }
    
    public static func query(predicate: NSPredicate? = nil) throws -> [NSManagedObject] {
        let context = try DataManager.getContext()
        let request = NSFetchRequest<NSFetchRequestResult>()
        request.entity = self.entity()
        request.predicate = predicate
        
        if let result = try? context.fetch(request){
            if let resultObject = result as? [NSManagedObject]{
                return resultObject
            }
        }
        throw Errors.wrongFetch
    }
    
    public static func all() throws -> [NSManagedObject] {
        return try query()
    }
    
    public static func deleteAll() throws {
        let managedContext = try DataManager.getContext()
        
        if let name = self.entity().name {
            let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: name)
            fetchRequest.returnsObjectsAsFaults = false
            
            do{
                let results = try managedContext.fetch(fetchRequest)
                for managedObject in results{
                    let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
                    managedContext.delete(managedObjectData)
                }
                try managedContext.save()
            } catch {
                throw Errors.cantDeleteObject
            }
        } else {
            throw Errors.wrongEntityName
        }
        
    }
}