UICollectionView Crashes with Error : Thread 1: EXC_BAD_ACCESS - ios

Question

Originally my CollectionView was working fine, but I wanted to adjust the width of the item in CollectionView according to the width of the TextLabel in CollectionView, so I added some code and then crashed when the program was initialized:
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "OnedaySubTodoCell", for: indexPath) as! SubCell
let width = 28 + cell.subNameLabel.bounds.size.width
print("Width: \(width)")
return CGSize(width: width, height: 20)
}
This is an error report and it show in class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterDelegate {:
Thread 1: EXC_BAD_ACCESS (code=1, address=0x7a00b0018)
This is output:
Width: 88.0
(lldb)
My class has inherited UICollectionViewDelegateFlowLayout，I want to know where the problem is.

Answer 1

As #rmaddy and #Prashant pointed out,
You should not use cellForItemAt in sizeForItemAT because
sizeForItemAt is called BEFORE initializing the cell in
cellForItemAt
And most probably that's the reason for your crash. Coming towards Solution.
I was faced with a similar problem (had to dynamically manage height) and what i did is something like
Calculate the estimated width of your label based on text. use the following string extension
//calculates the required width of label based on text. needs height and font of label
extension String {
func width(withConstrainedHeight height: CGFloat, font: UIFont) -> CGFloat {
let constraintRect = CGSize(width: .greatestFiniteMagnitude, height: height)
let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, attributes: [.font: font], context: nil)
return ceil(boundingBox.width)
}
}
Now, inside sizeForItemAt
//put actual lblHeight here
let lblHeight = Put_actual_label_height_here // e.g 30
//put actual label font here
let lblFont = Put_actual_label_font_here //e.g UIFont.boldSystemFont(ofSize: 20)
//calculate required label width
let lblRequiredWidth = yourLabel's_Text_String.width(withConstrainedHeight: lblHeight, font: lblFont)
//you may want to return size now
let height = yourItemsHeight
return CGSize(width: lblRequiredWidth, height: height)
Now that you have got the required width of your label, you can adjust the size of the item based on label's width.
Hope that helps. Let me know if you need any help. Thanks