Final version of ViewModel

ViewModel.swift

import UIKit
import Combine

class ViewModel
{
    var cancellables: Set<AnyCancellable> = []

    init()
    {
        $keyWordSearch.receive(on: RunLoop.main).debounce(for: .seconds(0.5), scheduler: RunLoop.main)
            .sink { (_) in
                self.fetchMovies()
            }.store(in: &cancellables)
    }
        
    let serviceProvider = Service.sharedInstance
    
    @Published var keyWordSearch: String = ""
    
    var diffableDataSource: MoviesTableViewDiffableDataSource!
    var snapshot = NSDiffableDataSourceSnapshot<String?, Result>()
    
    func fetchMovies()
    {
        serviceProvider.fetchFilms(for: keyWordSearch) { (results) in
            guard self.diffableDataSource != nil else { return }
            
            self.snapshot.deleteAllItems()
            self.snapshot.appendSections([""])
            
            if results.isEmpty
            {
                self.diffableDataSource.apply(self.snapshot, animatingDifferences: true)
                return
            }
        
            self.snapshot.appendItems(results, toSection: "")
            self.diffableDataSource.apply(self.snapshot, animatingDifferences: true)
        }
    }
}