object changes after function call

I have several objects created using the below code

name = "Toma"
    let toma = setupPet(name, family: "Hawn", stage: 1, imageName: "hawn_toma", imageNamef: "", imageNameEgg: "hawn_egg", hatchEXP: 5000, desc: "", eggDesc: "", rarity: "Common")


    name = "Hawn"
    let hawn = setupPet(name, family: "Hawn", stage: 2, imageName: "hawn", imageNamef: "", imageNameEgg: "hawn_egg", hatchEXP: 5000, desc: "", eggDesc: "", rarity: "Common")
    hawn.basePet = toma


    let tomaToHawn = NSEntityDescription.insertNewObjectForEntityForName("Evolution", inManagedObjectContext: self.appData.moc) as! Evolution
    tomaToHawn.evolveTo = hawn
    tomaToHawn.howEvolve = "Level"
    tomaToHawn.evolveValue = "10"


    NSLog("\(tomaToHawn.evolveTo!.name)")


    toma.addEvolveToObject(tomaToHawn)


    NSLog("\(tomaToHawn.evolveTo!.name)")

Now the result of the two NSLogs gives different values

Optional("Hawn")

Optional("Toma")

So it changed after the addEvolveToObject call. The method consists of

class Pet: NSManagedObject {
    func addEvolveToObject(value:Evolution) {
        let items = self.mutableSetValueForKey("evolveTo");
        items.addObject(value)
    }
}

The object is correct before the addObject call, but is incorrect after it

IE:

func addEvolveToObject(value:Evolution) {
    NSLog("********************************************************************")
    let items = self.mutableSetValueForKey("evolveTo");
    NSLog("Pet CD: \(value.evolveTo?.name)")
    items.addObject(value)
    NSLog("Pet CD: \(value.evolveTo?.name)")
    NSLog("********************************************************************")
}

Gives

Pet CD: Optional("Mel")

Pet CD: Optional("Joan")

Below are the full classes

Setup.swift

import UIKit
import CoreData
class Setup: NSObject {


    let appData : AppData = AppData.sharedInstance


    func setup() {
            // Hawn
        name = "Toma"
        let toma = setupPet(name, family: "Hawn", stage: 1, imageName: "hawn_toma", imageNamef: "", imageNameEgg: "hawn_egg", hatchEXP: 5000, desc: "", eggDesc: "", rarity: "Common")


        name = "Hawn"
        let hawn = setupPet(name, family: "Hawn", stage: 2, imageName: "hawn", imageNamef: "", imageNameEgg: "hawn_egg", hatchEXP: 5000, desc: "", eggDesc: "", rarity: "Common")
        hawn.basePet = toma


        let tomaToHawn = NSEntityDescription.insertNewObjectForEntityForName("Evolution", inManagedObjectContext: self.appData.moc) as! Evolution
        tomaToHawn.evolveTo = hawn
        tomaToHawn.howEvolve = "Level"
        tomaToHawn.evolveValue = "10"


        toma.addEvolveToObject(tomaToHawn)


        appData.saveContext()
    }
    func setupPet(name : String, family : String, stage : NSNumber, imageName : String, imageNamef : String, imageNameEgg : String, hatchEXP : NSNumber, desc : String, eggDesc : String, rarity : String) -> Pet {


        let pet : Pet = NSEntityDescription.insertNewObjectForEntityForName("Pet",inManagedObjectContext: appData.moc) as! Pet
        pet.name = name
        pet.family = family
        pet.stage = stage
        pet.imageName = imageName
        pet.imageNamef = imageNamef
        pet.imageNameEgg = imageNameEgg
        pet.hatchEXP = hatchEXP
        pet.rarity = rarity
        pet.desc = desc
        pet.eggDesc = eggDesc


        return pet
    }
}

Pet - core data properties class

import Foundation
import CoreData


extension Pet {


    @NSManaged var desc: String?
    @NSManaged var eggDesc: String?
    @NSManaged var family: String?
    @NSManaged var gained: NSNumber?
    @NSManaged var hatchEXP: NSNumber?
    @NSManaged var imageName: String?
    @NSManaged var imageNameEgg: String?
    @NSManaged var imageNamef: String?
    @NSManaged var name: String?
    @NSManaged var rarity: String?
    @NSManaged var stage: NSNumber?
    @NSManaged var adopt: NSSet?
    @NSManaged var evolveTo: NSSet?
    @NSManaged var userPets: NSSet?
    @NSManaged var basePet: Pet?


}

Pet

import Foundation
import CoreData

class Pet: NSManagedObject {
    func addEvolveToObject(value:Evolution) {
        let items = mutableSetValueForKey("evolveTo") as NSMutableSet;
        items.addObject(value)
    }
}

Evolution

import Foundation
import CoreData
extension Evolution {
    @NSManaged var evolveValue: String?
    @NSManaged var howEvolve: String?
    @NSManaged var evolveTo: Pet?
}

The pet class can take multiple evolution objects, each evolution object is for one pet