Invalid update: invalid number of items on UICollectionView

Question

I am stumped on this. Here is my scenario. In my Appdelegate, I am creating

1. An instance of a view controller that will be presented modally to collect two pi

Answer 1

I'm not practice with Obj-c so I write my answer in Swift.

supposing birthdays is an array of dates as String

birthdays = [String]()

func addDate() {
   birthdays.append("your_new_date")
   collectionView.insertItems(at: [IndexPath(item: birthdays.count - 1, section: 0)] ) 
}

func removeDate() {
   if birthdays.count > 0 {
      birthdays.removeLast() // use remove(at: Int) instead if u want
      collectionView.deleteItems(at: [IndexPath(item: birthdays.count, section: 0)] )
   }
}

You should avoid this error:

When the collectionview receives the notification I get the error:

'Invalid update: invalid number of items in section 0. The number of items contained in an existing section after the update (1) must be equal to the number of items contained in that section before the update (1), plus or minus the number of items inserted or deleted from that section (1 inserted, 0 deleted) and plus or minus the number of items moved into or out of that section (0 moved in, 0 moved out).'