Saving object to core data with NSPredicate - ios

Question

I'm trying to save an object to Core Data which is fetched from Parse, but i'd like only those which doesn't contain a name which is already in database:
func fetchFromParse() {
let entity = NSEntityDescription.entityForName("Medicine", inManagedObjectContext: context)
let query = PFQuery(className: "Medicine")
query.findObjectsInBackgroundWithBlock { (objects, error) -> Void in
if error == nil {
for object in objects! {
let medicine = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: self.context)
if let name = object["medicineName"] as? String,
amount = object["amountQuantity"] as? String {
let predicate = NSPredicate(format: "name != %#", name)
self.fetchRequest.predicate = predicate
do{
let fetchedEntities = try self.context.executeFetchRequest(self.fetchRequest) as! [Medicine]
//save to Core Data
medicine.setValue(name, forKey: "name")
medicine.setValue(amount, forKey: "amount")
} catch let error as NSError{
print(error)
}
do {
try self.context.save()
self.tableView.reloadData()
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
}
}
}
}
}
}
Fetch data from Core Data
func fetchFromCoreData() {
do {
let results = try context.executeFetchRequest(fetchRequest)
medicines = results as! [Medicine]
} catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
}
}
i put the in viewWillAppear:
if Reachability.isConnectedToNetwork() {
//fetching data from Parse
fetchFromParse()
fetchFromCoreData()
tableView.reloadData()
} else {
//fetching data from Core data
fetchFromCoreData()
logOutButton.enabled = false
}
But it doesn't work. Any suggestions how to repair it ?

Answer 1

You kind of have everything, just not hooked up. You shouldn't be instantiating and inserting the new object until after you've executed and checked the fetch. You currently execute the fetch but don't check to see if there is a duplicate. Both of these issues need to be resolved, something along the lines of:
let entity = NSEntityDescription.entityForName("Medicine", inManagedObjectContext: context)
let query = PFQuery(className: "Medicine")
query.findObjectsInBackgroundWithBlock { (objects, error) -> Void in
if error == nil {
for object in objects! {
if let name = object["medicineName"] as? String,
amount = object["amountQuantity"] as? String {
let predicate = NSPredicate(format: "name = %#", name)
self.fetchRequest.predicate = predicate
do{
let fetchedEntities = try self.context.executeFetchRequest(self.fetchRequest) as! [Medicine]
//save to Core Data
if fetchedEntities.count <= 0 {
let medicine = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: self.context)
medicine.setValue(name, forKey: "name")
medicine.setValue(amount, forKey: "amount")
}
} catch let error as NSError{
print(error)
}
}
}
do {
try self.context.save()
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
}
}
}