CODEWITHSUNDEEP
swiftxcodecore-data
incedible
incedible

Reputation: 5

CoreData - If something exists don't save it, if it doesn't exists then save it

I have a single entity Favourites and it contains values such as id, name but the problem is that it is creating multiple copies of items and I wanted it to only store values if it is unique. How can I do this with Core Data?

Here is my code:

let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
                
let newFav = Favourites(context: context)

if let id = self.itemsViewModel.items?.results?[indexPath.item].id {
   newFav.id = id
}

if let name = self.itemsViewModel.items?.results?[indexPath.item].name {
   newFav.name = name
}

self.saveItem()

I do this in an alert and outside of that closure is my saveItem() function everything works but I am trying to save only one item with one id. I am thinking of checking if that id exists but I am not quite sure how would I do that with CoreData

func saveItem() {
        do {
            let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
            try context.save()
        } catch {
            print("Error saving context \(error)")
        }
    }

Upvotes: 0

Views: 1743

Answers (1)

vadian
vadian

Reputation: 285079

Perform a fetch with a distinct predicate and create a new record if the result is zero, for example

func saveItem(with id : Int32, name : String) {
    do {
        let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
        let request : NSFetchRequest<Favourites> = Favourites.fetchRequest()
        request.predicate = NSPredicate(format: "id == %d AND name == %@", id, name)
        let numberOfRecords = try context.count(for: request)
        if numberOfRecords == 0 {
            let newFav = Favourites(context: context)
            newFav.name = name
            newFav.id = id
            try context.save()
        }
    } catch {
        print("Error saving context \(error)")
    }
}

Upvotes: 1

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