Is there any way we can restrict duplicate entries in core data?

Question

I have been trying to add objects in core data. So, i want that it should not allow duplicate entries in core data store. How to do that? This is my code related to save data.

Answer 1

I think the best approach would be to call the countForFetchRequest method using a predicate to evaluate whether your store has a matching object. Since this type of request does not pull back any objects it should be more performant than other solutions. Here is a Swift 2.0 implementation added to a NSManagedObject subclass.

  func tokenExists (aToken:String) -> Bool {
        let request: NSFetchRequest = NSFetchRequest(entityName: self.className!)

        let predicate = NSPredicate(format: "token == %@", argumentArray: [aToken])

        request.predicate = predicate

        let error: NSErrorPointer = nil

        let count = self.managedObjectContext!.countForFetchRequest(request, error: error)

        if count == NSNotFound {
            return false
        }
        return true
    }

NB - (One could substitute any equality criteria you like for the predicate but keep in mind that if possible you should use a numerical identifier if one is available ~ for best performance)

Usage:

One might then use the function above during the insertion:

func insertToken (value:String) {

        if  !tokenExists(value) {
            self.token = value
            saveState()
        }

    }