How to update existing object in core data ? [Swift]

Question

I have preloaded data from a .csv file into coredata. I am fetching the data in the following way

var places:[Places] = []

in viewDidLoad :

if let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext {
            let fetchRequest = NSFetchRequest(entityName: "Places")
            do{
                places = try managedObjectContext.executeFetchRequest(fetchRequest) as! [Places]
            }

            catch let error as NSError{
                print("Failed to retrieve record: \(error.localizedDescription)")
            }
        }

In the data there is an attribute isFavorite of type String whose initial value is false. I am changing the value of isFavorite on button click. I want to save the changes made by the user. How can i make this change persistent ?

Here is my button action

@IBAction func addToFavourites(sender: AnyObject) {

        cell = tableView.cellForRowAtIndexPath(NSIndexPath(forRow: sender.tag, inSection: 0)) as! CustomTableViewCell
        if cell.isFavouriteLabel.text! == "false" {
            cell.isFavouriteLabel.text = "true"

        }else if cell.isFavouriteLabel.text == "true"{
            cell.isFavouriteLabel.text = "false"

        }
}

Basically i want to set the value of places.isFavourite = cell.isFavoriteLabel.text and save to core data

EDIT : if i try this inside my button action method

if let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext {

            let place : Places = Places()
            place.isFavourite = cell.isFavouriteLabel.text
             do{
                try managedObjectContext.save()
            } catch let error as NSError{
                print(error)

            }
          }

i am getting an error : Failed to call designated initializer on NSManagedObject class

if i simply add this code in the button action method

places.isFavourite = cell.isFavouriteLabel.text

i get this error : [Places] does not have a member named isFavourite

MirekE · Accepted Answer · 2015-09-01 18:11:12Z

3

Your current code is:

if let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext {

            let place : Places = Places()
            place.isFavourite = cell.isFavouriteLabel.text
             do{
                try managedObjectContext.save()
            } catch let error as NSError{
                print(error)

            }
          }

That would create a new place (if it worked), but you need to update an existing one.

You have the places returned from managedObjectContext.executeFetchRequest.

So you need to get something like places[index_of_the_cell_in_question].isFavourite = cell.isFavouriteLabel.text

and then managedObjectContext.save().

answered Sep 1, 2015 at 18:11

MirekE

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1 Comment

sunny k Over a year ago

thanx places[sender.tag].isFavourite = cell.isFavouriteLabel.text did the trick

Bart Hopster · Accepted Answer · 2015-09-01 08:33:03Z

0

Use the save function of the NSManagedObjectContext:

places.isFavourite = cell.isFavoriteLabel.text

var error: NSError?
if managedObjectContext.save(&error) != true {
    // Error
}

answered Sep 1, 2015 at 8:33

Bart Hopster

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3 Comments

sunny k Over a year ago

i can't seem to access isFavourite using places.isFavourite in my button action method

Bart Hopster Over a year ago

Dependent on your implementation, you should be able to access the corresponding Places object after clicking the button. Your button action method has a sender parameter, maybe you can use that.

sunny k Over a year ago

i can access isFavorite if places is declared like this var places : Places!

Jérôme Demyttenaere · Accepted Answer · 2015-09-01 08:35:40Z

This is simple as this:

Find the entry you want to modify in places then save the core data context.

func saveContext () {
    if let moc = self.managedObjectContext {
        var error: NSError? = nil
        if moc.hasChanges && !moc.save(&error) {
            // Replace this implementation with code to handle the error appropriately.
            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            println("Unresolved error \(error), \(error!.userInfo)")
            abort()
        }
    }
}

I suggest you used a manager to insert, fetch and delete entry in your core data.

import Foundation
import CoreData

class CoreDataHelper: NSObject {

    class var shareInstance:CoreDataHelper {
        struct Static {
            static let instance:CoreDataHelper = CoreDataHelper()
        }
        return Static.instance
    }

    //MARK: - Insert -
    func insertEntityForName(entityName:String) -> AnyObject {
        return NSEntityDescription.insertNewObjectForEntityForName(entityName, inManagedObjectContext: self.managedObjectContext!)
    }

    //MARK: - Fetch -
    func fetchEntitiesForName(entityName:String) -> NSArray {
        ...
    }

    //MARK: - Delete -
    func deleteObject(object:NSManagedObject) {
        self.managedObjectContext!.deleteObject(object)
    }

    // MARK: - Core Data Saving support -
    func saveContext () {
        if let moc = self.managedObjectContext {
            var error: NSError? = nil
            if moc.hasChanges && !moc.save(&error) {
                // Replace this implementation with code to handle the error appropriately.
                // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                println("Unresolved error \(error), \(error!.userInfo)")
                abort()
            }
        }
    }

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