When I return 1 in numberOfItemsInSection cellForItemAt not called in Swift

I am new in Swift and I am facing a problem with collection view. When I am returning 1 in numberOfItemsInSection cellForItemAt not call but when I return 2 it get call. I am not able to understand problem. Delegate and protocol are also correct.

My code is like this:

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return arrSelectedSchoolIds.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        
        let cell = CollectionViewFilter.dequeueReusableCell(withReuseIdentifier: "SchoolLogo", for: indexPath as IndexPath) as! SchoolLogo
           cell.imgSchoolLogo.image = getSchoolLogo(schoolID: arrSelectedSchoolIds[indexPath.row])
           return cell
        }


func getSchoolLogo(schoolID:String?) -> UIImage
{
    switch schoolID
    {
    case "1":
        return UIImage(named: "image1")!
    case "2":
        return UIImage(named: "image2")!
    case "3":
        return UIImage(named: "image3")!
    case "4":
        return UIImage(named: "image4")!
    case "5":
        return UIImage(named: "image5")!
    case "6":
        return UIImage(named: "image6")!
    default:
        return UIImage(named: "defaultimage")!
    }
}

Images are added in Assest file.

I had the same problem. this happened when the collectionView scroll direction is horizontal and the height of collectionView is less than 50. I increased the collectionView height to 50 and the problem solved.

The cellForItemAtIndexPath will not get called if you do not provide the content size information to the collection view. If you are using Flow layout, You need to set the item sizes properly.