numberOfItemsInSection func calling before viewdidload()

Question

Here I am first retrieving an image from firebase then adding it to an locationImage array,which will be later added to collectionView.

import UIKit
import Firebase
import FirebaseStorage

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {

var locationImage = [UIImage(named: "hawai"), UIImage(named: "mountain")]

override func viewDidLoad() {
    super.viewDidLoad()

    retrieveData()
}


func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    print(locationImage.count)
    return locationImage.count
}
func retrieveData(){
    let database = FIRDatabase.database().reference()
    let storage = FIRStorage.storage().reference()

    let imageRef = storage.child("blue blurr.png")

    imageRef.data(withMaxSize: (1*1000*1000)) { (data, error) in
        if error == nil{

            let tempImage = UIImage(data: data!)
            self.locationImage.append(tempImage)
            print("HELLLLLOOOO WOOOOORRRLLLDDDD")
            print(self.locationImage.count)
        }
        else{
            print(error?.localizedDescription)
        }
    }
    return
}

}

Here the retrieveData() function is calling before collectionView().Instead viewdidload should be called first,how can I do that,can someone help ?

Set collectionView datasource in viewDidLoad after retrieve data. Don't set in storyboard — Rohi, Mar 14 '18 at 10:18
Remove Datasource and delegate from IB and set them inside retrieve data after loading your data. @Qazi Shahood — Shivam Tripathi, Mar 14 '18 at 10:45
ViewDidLoad should definitely not be called first. This is expected behaviour. It runs asynchronously. You should pass the data before the controller is loaded... — Dominik Bucher, Mar 14 '18 at 11:19

score 4 · Accepted Answer · answered Mar 14 '18 at 11:22

You don't want the collectionView to be called before ViewDidLoad?

override func viewDidLoad() {
    super.viewDidLoad()

    collectionView.dataSource = self
    collectionView.delegate = self
}

But this shouldn't worry you, because if the array you are using to initialise the CollectionView is empty, it wouldn't matter if the call goes to the numberOfItemsInSection method.

What you require here is to call a reload after you have data in your locationImage. So right after your self.locationImage.append(tempImage), add:

self.collectionView.reloadData()

score 0 · Answer 2 · answered Mar 14 '18 at 11:23

import UIKit
import Firebase
import FirebaseStorage

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {

var locationImage = [UIImage(named: "hawai"), UIImage(named: "mountain")]

override func viewDidLoad() {
    super.viewDidLoad()

    retrieveData()

    //Add these two line here remove delegate and datasource from storyborad
    collectionView.dataSource = self
    collectionView.delegate = self
}


func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    print(locationImage.count)
    return locationImage.count
}
func retrieveData(){
    let database = FIRDatabase.database().reference()
    let storage = FIRStorage.storage().reference()

    let imageRef = storage.child("blue blurr.png")

    imageRef.data(withMaxSize: (1*1000*1000)) { (data, error) in
        if error == nil{

            let tempImage = UIImage(data: data!)
            self.locationImage.append(tempImage)
            print("HELLLLLOOOO WOOOOORRRLLLDDDD")
            print(self.locationImage.count)
        }
        else{
            print(error?.localizedDescription)
        }
    }
    return
}

}

score 0 · Answer 3 · answered Mar 14 '18 at 13:31

100% working

Where is your IBOutlet for UICollectionView?

 @IBOutlet weak var collectionView: UICollectionView!

Set first IBOutlet & try this code:

import UIKit
import Firebase
import FirebaseStorage

 class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {

var locationImage = [UIImage(named: "hawai"), UIImage(named: "mountain")]

override func viewDidLoad() {
super.viewDidLoad()
 //Add these two line here remove delegate and datasource from storyborad
collectionView.dataSource = self
collectionView.delegate = self
retrieveData()
}


 func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

print(locationImage.count)
return locationImage.count
 }
 func retrieveData(){
let database = FIRDatabase.database().reference()
let storage = FIRStorage.storage().reference()

let imageRef = storage.child("blue blurr.png")

imageRef.data(withMaxSize: (1*1000*1000)) { (data, error) in
    if error == nil{

        let tempImage = UIImage(data: data!)
        self.locationImage.append(tempImage)
        print("HELLLLLOOOO WOOOOORRRLLLDDDD")
        print(self.locationImage.count)
    }
    else{
        print(error?.localizedDescription)
    }
}
return
}

score -2 · Answer 4 · edited Oct 28 '20 at 13:44

-2

a simple solution is that put sleep your function for some sec something like this

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    do {
        sleep(1)
    }

EDIT: formatted function

edited Oct 28 '20 at 13:44

Apps-n-Add-Ons

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answered Oct 28 '20 at 12:33

Sheikh Usman

11
3

Never ever do that!! – vadian Oct 28 '20 at 14:09

numberOfItemsInSection func calling before viewdidload()

4 Answers4