CatsViewController.swift

import UIKit
import Purchases

class CatsViewController: UIViewController {
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 1. Add an observer for our kPurchaserInfoUpdated notification that triggers a function to update the view
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(updateViewForPurchaserInfo),
                                               name: NSNotification.Name("kPurchaserInfoUpdated"), object: nil)
        
        updateViewForPurchaserInfo()

    }
    
    // 2. Create a function that will update the state of your view based on the PurchaserInfo status
    @objc func updateViewForPurchaserInfo() {
        Purchases.shared.purchaserInfo { (purchaserInfo, error) in
            self.configureCatContentFor(purchaserInfo: purchaserInfo)
        }
    }
    
    func configureCatContentFor(purchaserInfo: Purchases.PurchaserInfo?) {
        
        // set the content based on the user subscription status
    }
    
    // 3. Remove the observer when the view is deallocated
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
}