Swift: NSCollectionViewItem properties not change

Question

I am building a Cocoa Swift app which have NSCollectionViews and have an NSCollectionView which has custom NSCollectionViewItem which has like below as in photo.

My purpose is building something like a calendar and as you understand from the image, I want to change date value and date string. Even tried it like below couldn't achieve it and did not understand what effects it.

Here is my custom NSCollectionViewItem

class CalendarDateCell: NSCollectionViewItem {

    
    @IBOutlet weak var dateNameString: NSTextField!
    @IBOutlet weak var dateNumberString: NSTextField!
    
    
    override func loadView() {
        super.loadView()
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do view setup here.
    }
    
}

Here is my itemForRepresentedObjectAt function.

func collectionView(_ collectionView: NSCollectionView, itemForRepresentedObjectAt indexPath: IndexPath) -> NSCollectionViewItem {
        // 4
        let item = calendarCollectionView.makeItem(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "CalendarDateCell"), for: indexPath)
        guard let collectionViewItem = item as? CalendarDateCell else {return item}
        
        
        
        switch indexPath.item % 3 {
        case 0,1:
            collectionViewItem.dateNameString.stringValue = "0-1"
        case 2:
            collectionViewItem.dateNameString.stringValue = "3"
        default:
            break
        }
        
        return collectionViewItem
    }

I tried it for testing, UI is done work but I did not change the property of the NSCollectionViewItem as a change of NSIndexPath

Then I added a String variable to NSCollectionViewItem and observe it with didSet method and I can change the variable but it's not effective for UI elements of AppKit.

How can I fix the problem? Any suggestions?

Edit:

I add a model for NSCollectionViewItem

var calendarModel: CalendarModel = CalendarModel() {
        didSet {
            dateNameString.stringValue = calendarModel.name
        }
    }

Then change it in controller as

collectionViewItem.calendarModel.name = "1231"

but never affects.

Thanks in advance