Operation is invalid after previous operation - ios

Question

I am making some good progress on my social networking application. I have run into an issue. I have a ViewController that provides a TableView that is populated with content from my parse database. In the cells I have a RSVP button that is supposed to send a RSVP based on the indexPath to the database when clicked and remove when it is clicked again. I believe my logic is correct, however, I keep receiving the error:
Operation is invalid after previous operation.
I placed a breakpoint to locate the cause of the crash and I have identified that it is happening at the addUniqueObject line within the rsvpButtonClicked IBOutlet function.
Can someone help me? My code is below.
import UIKit
import CoreLocation
class MainFeedViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
#IBOutlet var eventsTable: UITableView!
var user = PFUser.currentUser()
var refresher: UIRefreshControl!
var eventId = [String]()
var eventNames = [String]()
var eventCity = [String]()
var imageFiles = [PFFile]()
var getEventsQuery = 0
var userRsvps = [NSArray]()
var rsvp = 0
override func viewDidLoad() {
super.viewDidLoad()
getuserlocation()
getTodayDate()
}
override func viewWillAppear(animated: Bool) {
refreshControl()
//getMyRsvps()
}
override func viewDidAppear(animated: Bool) {
let timer = NSTimer.scheduledTimerWithTimeInterval(2.0, target: self, selector: "eventQuery", userInfo: nil, repeats: false)
}
func getMyRsvps() {
var getRsvps = PFUser.query()
getRsvps.whereKey("objectId", equalTo: user.objectId)
getRsvps.whereKeyExists("myrsvp")
getRsvps.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]!, error: NSError!) -> Void in
if error == nil {
self.userRsvps.append(objects)
}
}
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.eventsTable.dequeueReusableCellWithIdentifier("mainFeedContent") as MainFeedContentTableViewCell
cell.eventName.text = eventNames[indexPath.row]
imageFiles[indexPath.row].getDataInBackgroundWithBlock{
(imageData: NSData!, error: NSError!) -> Void in
if error == nil {
let image = UIImage(data: imageData)
cell.eventImage.image = image
}
}
cell.rsvpButton.tag = indexPath.row
cell.rsvpButton.addTarget(self, action: "rsvpButtonClick:", forControlEvents: UIControlEvents.TouchUpInside)
return cell
}
#IBAction func rsvpButtonClick(sender: UIButton) {
var senderButton = sender
println("Current row \(senderButton.tag)")
var tempObject = eventId[senderButton.tag]
println("\(tempObject)")
PFUser.currentUser().addUniqueObject(tempObject, forKey: "myrsvp")
PFUser.currentUser().saveInBackground()
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return eventId.count
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let mainViewIdentifier = "showDetail"
if segue.identifier == mainViewIdentifier {
if let destination = segue.destinationViewController as? DetailViewController {
if let feedIndex = eventsTable.indexPathForSelectedRow()?.row {
destination.eventNames = eventNames[feedIndex]
destination.eventId = eventId[feedIndex]
destination.eventImagesFile = imageFiles[feedIndex]
}
}
}
}
func eventQuery() {
let getEventsQuery = PFQuery(className: "Events")
getEventsQuery.whereKey("eventLocation", nearGeoPoint: user["location"] as PFGeoPoint, withinMiles: user["preferredDistanceEvents"] as Double)
getEventsQuery.limit = 16
getEventsQuery.findObjectsInBackgroundWithBlock {(objects: [AnyObject]!, error: NSError!) -> Void in
if error == nil {
println("Successfully retrieved \(objects.count) events")
for object in objects {
self.eventId.append(object.objectId)
self.eventNames.append(object["eventName"] as String)
self.eventCity.append(object["eventCity"] as String)
self.imageFiles.append(object["eventPicture"] as PFFile)
self.eventsTable.reloadData()
}
} else {
println(error)
}
}
}
func refreshControl() {
refresher = UIRefreshControl()
refresher.attributedTitle = NSAttributedString(string: "Pull to refresh")
refresher.addTarget(self, action: "refresh", forControlEvents: UIControlEvents.ValueChanged)
self.eventsTable.addSubview(refresher)
}
/*
func scrollViewDidEndDragging(scrollView: UIScrollView, willDecelerate decelerate: Bool) {
var height: CGFloat = scrollView.frame.size.height
var contentYoffset: CGFloat = scrollView.contentOffset.y
var distanceFromBottom: CGFloat = scrollView.contentSize.height - contentYoffset
if distanceFromBottom <= height {
println("End of Table")
refresh()
}
}
*/
func refresh() {
self.getEventsQuery++
if self.getEventsQuery < self.eventId.count {
let refreshEventsQuery = PFQuery(className: "Events")
refreshEventsQuery.whereKey("location", nearGeoPoint: user["location"] as PFGeoPoint, withinMiles: user["preferredDistanceEvents"] as Double)
refreshEventsQuery.whereKey("objectId", notContainedIn: eventId)
refreshEventsQuery.limit = 4
refreshEventsQuery.findObjectsInBackgroundWithBlock {(objects: [AnyObject]!, error: NSError!) -> Void in
if error == nil {
println("Successfully retrieved \(objects.count) events")
for object in objects {
self.eventNames.append(object["eventName"] as String)
self.eventCity.append(object["City"] as String)
self.imageFiles.append(object["eventPicture"] as PFFile)
self.eventId.append(object.objectId)
self.eventsTable.reloadData()
}
} else {
println(error)
}
}
} else {
println("No More Events. Sorry")
}
self.refresher.endRefreshing()
}
func getuserlocation() {
PFGeoPoint.geoPointForCurrentLocationInBackground { (geopoint: PFGeoPoint!, error: NSError!) -> Void in
if error == nil {
self.user["location"] = geopoint
self.user.saveInBackground()
}
}
}
func getTodayDate(){
var today = NSDate()
var calendar = NSCalendar.currentCalendar()
var flags = NSCalendarUnit.HourCalendarUnit | NSCalendarUnit.MinuteCalendarUnit
var components = calendar.components(flags, fromDate: today)
var hour = components.hour
var minutes = components.minute
println("Today is \(today). The time is \(hour):\(minutes)")
}
}

Answer 1

I think this is a bug in parse (in code shared with JS, because I've experienced the problem there). Specifically, this failure appears when intermixing the add and remove PFObject methods to manipulate array columns.
I've used both of the following workarounds with some success:
Delimit adds and removes with intervening saves. In other words, build your own addToColAndSave and removeFromColAndSave convenience methods. If you've called one of them, don't call the other until the save completes.
Probably easier: restructure the code to avoid the add/remove methods on arrays. Instead, use the getter (get in JS, objectForKey: in iOS) to get the array in memory, then manipulate it natively. Use the sdk setter to update the object.