MVC - NSFetchRequest in model file without UIKit - ios

Question

In my ViewController, I have a function for fetching all the 'headingNumbers' (an attribute of the entity 'Vocabulary'). I understood that this is not good MVC practice.
So I created a new swift file.
I did not import UIKit. Youtube Stanford - Developing iOS 9 Apps with Swift - 2, 22:53: "Never import UI KIT in a model file because the model is UI independent"
(https://www.youtube.com/watch?v=j50mPzDMWVQ)
However, now I get these messages like
"Use of unresolved identifier 'UIApplication'".
Which makes sense, as I did not import the UIKit.
The question is: how do I now execute a fetch request in my new swift file.
(As you probably now by now, I am a beginner)
import Foundation
import CoreData
class QueryData {
private var selectedHeadingNumber:String = "-123456789"
private var setOfHeadingNumbers:[String] = [String]()
func getHeadingNumbers2() -> [String] {
if let managedObjectContext = (UIApplication.sharedApplication().delegate as? AppDelegate)?.managedObjectContext {
// Create Fetch Request
let fetchRequest = NSFetchRequest(entityName: "Vocabulary")
// Add Sort Descriptor
let sortDescriptor = NSSortDescriptor(key: "headingNumber", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
// Execute Fetch Request
do {
let result = try managedObjectContext.executeFetchRequest(fetchRequest)
for managedObject in result {
if let foundHeadingNumber = managedObject.valueForKey("headingNumber") {
if let result_number = foundHeadingNumber as? NSNumber
{
let result_string = "\(result_number)"
if !setOfHeadingNumbers.contains(result_string) {
print("Headingnumber: \(foundHeadingNumber) ")
setOfHeadingNumbers.append(result_string)
print("updated selectedHeadingNumber: ", selectedHeadingNumber)
selectedHeadingNumber = result_string
// set the default lessonnumber to the first lesson
if selectedHeadingNumber == "-123456789" {
selectedHeadingNumber = result_string
print("updated selectedHeadingNumber: ", selectedHeadingNumber)
}
}
}
//setOfHeadingNumbers.append(first)
}
}
} catch {
let fetchError = error as NSError
print(fetchError)
}
} // end of if statement
return setOfHeadingNumbers
} // end of func
} // end of class

Answer 1

What you actually need is NSManagedObjectContex. Pass it as an argument to method:
func getHeadingNumbers2(inContext context: NSManagedObjectContext) -> [String]
{
...
}
Or inject it as dependency in initializer
class QueryData
{
let context: NSManagedObjectContext
init(context: NSManagedObjectContext)
{
self.context = context
}
func getHeadingNumbers2() -> [String]
{
let fetchRequest = NSFetchRequest(entityName: "Vocabulary")
let result = try self.context.executeFetchRequest(fetchRequest)
...
}
}