CODEWITHSUNDEEP
iosswiftcore-data
Yafet Shil
Yafet Shil

Reputation: 41

I want to fetch data from CoreData and if the data exist I want to return true, if not I want to return false

I want to fetch data from CoreData and if the data exist I want to return true, if not I want to return false, I'm working on Favoris, so I want to fetch if the event id exists in CoreData, if it does i want to return true and if not it will return false, there is my code:

    func  retrieveFavoris() {

            //As we know that container is set up in the AppDelegates so we need to refer that container.
            guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }

            //We need to create a context from this container
            let managedContext = appDelegate.persistentContainer.viewContext

            //Prepare the request of type NSFetchRequest  for the entity
            let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Favoris")


            do {
                let result = try managedContext.fetch(fetchRequest)
                for data in result as! [NSManagedObject] {
                    print(data.value(forKey: "id_event") as! String)
                }

            } catch {

                print("No Favoris")
            }
        }

PS: my xcdata file contains one Entity "Favoris" which contains only one attribute "id_event"

I want to test if id event exists in CoreData, so i think i have to pass in parameters an event_id that i enter and then test if it exist, so the function should return a boolean value true if exist and false if does not exist.

Any help please? Thank you

Upvotes: 0

Views: 81

Answers (2)

Kirti Nikam
Kirti Nikam

Reputation: 2206

If you want to check only data is exists or not then use result.count:

func  retrieveFavoris() -> Bool {

        //As we know that container is set up in the AppDelegates so we need to refer that container.
        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }

        //We need to create a context from this container
        let managedContext = appDelegate.persistentContainer.viewContext

        //Prepare the request of type NSFetchRequest  for the entity
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Favoris")
        let predicate = NSPredicate(format: "id_event = %@", id_event_value)
        fetchRequest.predicate = predicate
        do {
            let result = try managedContext.fetch(fetchRequest)
            return (result.count > 0)
        } catch {
            print("No Favoris")
            return false
        }
    }

Upvotes: 0

vadian
vadian

Reputation: 285079

You have to add a parameter, a return type and a predicate for the id event.

func retrieveFavoris(idEvent: Int) -> Bool {

        //As we know that container is set up in the AppDelegates so we need to refer that container.
        let appDelegate = UIApplication.shared.delegate as! AppDelegate

        //We need to create a context from this container
        let managedContext = appDelegate.persistentContainer.viewContext

        //Prepare the request of type NSFetchRequest  for the entity
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Favoris")
        fetchRequest.predicate = NSPredicate(format: "id_event = %ld", idEvent)
        do {
            return try !managedContext.fetch(fetchRequest).isEmpty
        } catch {
            print("No Favoris", error)
            return false
        }
}

Upvotes: 1

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