Array isn't updating in Swift

Question

When you start the application, you should get a line from the Firestore documents and write to an array, (array)

    var items = [String]()

override func viewDidLoad() {
        let db = Firestore.firestore()
        db.collection("cities").getDocuments() { (querySnapshot, err) in
            if let err = err {
                print("Error getting documents: \(err)")
            } else {
                for document in querySnapshot!.documents {
                    print("\(document.documentID) => \(document.data())")
                    self.items.append(document.data()["title"] as! String)
                }
            }
        }

    }

then in the cell creation function, the text should be changed to a line from the array.

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as! colCell
        print(self.items)
        cell.myLabel.text = self.items[indexPath.item]

        return cell
    }

But the array with strings from the firestore is not updated in the cell creation function. Why?

(I printed out array in viewDidLoad and in cell, it's updated in viewDidLoad and not updated in cell)

did you call collectionView.reloadData?

Quoc Nguyen
– Quoc Nguyen

2019-03-24 23:48:24 +00:00
Commented Mar 24, 2019 at 23:48 — Quoc Nguyen
– Quoc Nguyen, Commented Mar 24, 2019 at 23:48

Shehata Gamal · Accepted Answer · 2019-03-24 23:53:16Z

2

You need to reload the collectionView as the call to firestore is asynchronous

for document in querySnapshot!.documents {
   print("\(document.documentID) => \(document.data())")
   self.items.append(document.data()["title"] as! String)
}
self.collectionView.reloadData()

edited Mar 24, 2019 at 23:53

answered Mar 24, 2019 at 23:48

Shehata Gamal

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Comments

Ani · Accepted Answer · 2019-03-25 03:09:47Z

0

You can reload the given cell after updating the date like this,

collectionView.reloadItemsAtIndexPaths(arrayOfIndexPaths)

it is optimised way to update UICollectionView.

answered Mar 25, 2019 at 3:09

Ani

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