Some useful core data extensions + threading

CoreDataExtensions.swift

import UIKit
import CoreData

public class Mappable : NSManagedObject {
    
    var className: String {
        return String(describing: type(of: self))
    }
    
    class var className: String {
        return String(describing: self)
    }
    
    static var entityName: String {
        return self.className //insead of `entity().name!`
    }
    
    func mapProperties(_ dict:NSDictionary) {
        
    }
    
    class func create(context:NSManagedObjectContext) -> Mappable {
        let entityName = self.entityName
        let entity = NSEntityDescription.insertNewObject(forEntityName: entityName, into: context) as! Mappable
        return entity
    }
    
    class func upsert(predicate:NSPredicate, context:NSManagedObjectContext, data:NSDictionary) -> Mappable {
        if let entity = fetch(withPredicate: predicate, inContext: context)?.first {
            entity.mapProperties(data)
            return entity
        } else {
            let newEntity = create(context: context)
            newEntity.mapProperties(data)
            return newEntity
        }
    }
    
    
    private class func fetch(fetchRequest:NSFetchRequest<NSFetchRequestResult>, context:NSManagedObjectContext) -> [Mappable]?{
        do {
            let results = try context.fetch(fetchRequest) // TODO : this errors out
            let entities = results as! [Mappable]
            
            if results.count == 0 {
                return nil
            } else {
                return entities
            }
        } catch let error as NSError {
            print("Could not fetch \(error), \(error.userInfo)")
            return nil
        }
    }
    
    class func fetchAll(inContext context:NSManagedObjectContext) -> [Mappable]? {
        let entityName = self.entityName
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        return self.fetch(fetchRequest: fetchRequest, context: context)
    }
    
    class func fetch(withPredicate predicate:NSPredicate, inContext context:NSManagedObjectContext) -> [Mappable]? {
        let entityName = self.entityName
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        fetchRequest.predicate = predicate
        return self.fetch(fetchRequest: fetchRequest, context: context)
    }
    
    
    class func fetch(_ property:String, _ value:String, _ context:NSManagedObjectContext) -> Mappable? {
        let entityName = self.entityName
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        let predicate: NSPredicate = NSPredicate(format: "\(property) == %@", value)
        fetchRequest.predicate = predicate
        return self.fetch(fetchRequest: fetchRequest, context: context)?.first
    }
    
    func inContext(context:NSManagedObjectContext) -> Mappable?  {
        var objectID = self.objectID
        if let entity = context.object(with: objectID) as? Mappable {
            return entity
        } else {
            return nil
        }
    }
    
    class func count(context:NSManagedObjectContext) -> Int {
        let entityName = self.entityName
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        //var predicate = NSPredicate(format: "status != 'Read' && fromBarchick == YES")
        //fetchRequest.predicate = predicate
        
        let count =  try! context.count(for: fetchRequest)
        return count
    }
    
    class func count(predicate:NSPredicate, context:NSManagedObjectContext) -> Int {
        let entityName = self.entityName
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        fetchRequest.predicate = predicate
        
        let count =  try! context.count(for: fetchRequest)
        return count
    }
    
    class func delete(_ property:String, _ value:String, _ context:NSManagedObjectContext) {
        let entityName = self.entityName
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        let predicate: NSPredicate = NSPredicate(format: "\(property) == %@", value)
        fetchRequest.predicate = predicate
        
        do
        {
            let results = try context.fetch(fetchRequest)
            for managedObject in results
            {
                let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
                context.delete(managedObjectData)
            }
        } catch let error as NSError {
            print("Detele all data in \(entityName) error : \(error) \(error.userInfo)")
        }
        
    }
    
    
    class func deleteAll(){
        let managedContext = Cholent.getContext()
        let entityName = self.entityName
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        
        fetchRequest.returnsObjectsAsFaults = false
        do
        {
            let results = try managedContext.fetch(fetchRequest)
            for managedObject in results
            {
                let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
                managedContext.delete(managedObjectData)
            }
        } catch let error as NSError {
            print("Detele all data in \(entityName) error : \(error) \(error.userInfo)")
        }
    }
    
    
    class func deleteAll(context:NSManagedObjectContext){
        
        let managedContext = context
        let entityName = self.entityName
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        
        fetchRequest.returnsObjectsAsFaults = false
        do
        {
            let results = try managedContext.fetch(fetchRequest)
            for managedObject in results
            {
                let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
                managedContext.delete(managedObjectData)
            }
        } catch let error as NSError {
            print("Detele all data in \(entityName) error : \(error) \(error.userInfo)")
        }
    }
    
}


class Cholent {
    var mainContext = (UIApplication.shared.delegate as! AppDelegate).managedObjectContext
    
    class func getContext() -> NSManagedObjectContext {
        return (UIApplication.shared.delegate as! AppDelegate).managedObjectContext
    }
    
    func saveContext(){
        self.mainContext.performAndWait {
            do {
                try self.mainContext.save()
            } catch {
                fatalError("Failure to save context: \(error)")
            }
        }
    }
    
    func perform(operation:@escaping (_ context:NSManagedObjectContext) -> (), completed:@escaping ()->()) {
        
        let backgroundContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
        backgroundContext.parent = mainContext
        
        
        backgroundContext.perform {
            operation(backgroundContext)
            
            do {
                try backgroundContext.save()
                self.mainContext.performAndWait {
                    do {
                        try self.mainContext.save()
                        completed()
                    } catch {
                        fatalError("Failure to save context: \(error)")
                    }
                }
            } catch {
                fatalError("Failure to save context: \(error)")
            }
            
            
        }
        
    }
}