CoreDataHelper.swift

extension NSManagedObject{
    
    static func createItem(moc: NSManagedObjectContext, entityName: String) -> NSManagedObject {
        return NSEntityDescription.insertNewObjectForEntityForName( entityName, inManagedObjectContext: moc)
    }
    
    static func getListOfItems(moc: NSManagedObjectContext, entityName: String) -> [NSManagedObject]? {
        
        let fetchRequest = NSFetchRequest(entityName: entityName)
        do {
            
            let results = try moc.executeFetchRequest(fetchRequest)
            return results as? [NSManagedObject]
            
        } catch let error as NSError {
            print("Could not fetch \(error), \(error.userInfo)")
            return nil
        }
        
    }
    
    static func getItemsWhere(moc: NSManagedObjectContext, entityName: String, fieldsAndValues: [(String, String)]) -> [NSManagedObject]? {
        
        let fetchRequest = NSFetchRequest(entityName: entityName)
        let predicates = fieldsAndValues.map { (fieldAndValue:(String, String))-> NSPredicate in
            return NSPredicate(format:"\(fieldAndValue.0)==%@", fieldAndValue.1)
        }
        fetchRequest.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: predicates)
        do {
            
            let results = try moc.executeFetchRequest(fetchRequest)
            return results as? [NSManagedObject]
           
            
            
        } catch let error as NSError {
            print("Could not fetch \(error), \(error.userInfo)")
            return nil
        }

    
    }
    
    static func getItem(moc: NSManagedObjectContext, entityName: String, keyField: String, value: String) -> NSManagedObject? {
        
        let fetchRequest = NSFetchRequest(entityName: entityName)
        fetchRequest.predicate = NSPredicate(format:"\(keyField)==%@", value)
        
        do {
            
            let results = try moc.executeFetchRequest(fetchRequest)
            if results.count == 0 {
                print("There are no item with this value")
            } else if results.count > 1 {
                print("There is more than one item with this value")
            } else {
                return results[0] as? NSManagedObject
            }
            return nil
            
        } catch let error as NSError {
            print("Could not fetch \(error), \(error.userInfo)")
            return nil
        }
    }
}