updating comments

Signed-off-by: Matt Bruce <mbrucedogs@gmail.com>

EmployeeDirectory/Models/Employee.swift

@@ -27,7 +27,7 @@ public enum EmployeeType: String, Codable, CustomStringConvertible {
 /// Employee Object
 /// JSON Object defintion
 /// - https://square.github.io/microsite/mobile-interview-project/
-public struct Employee: Codable {
+public struct Employee: Hashable, Codable {
     
     /// The unique identifier for the employee. Represented as a UUID.
     public let uuid: UUID

EmployeeDirectory/ViewControllers/EmployeesViewController.swift

@@ -34,24 +34,46 @@ class EmployeesViewController: UIViewController {
     // Prevents multiple calls during rapid scrolling
     private var isFetchingNextPage: Bool = false
 
+    private var dataSource: UITableViewDiffableDataSource<Int, Employee>!
+
     // MARK: - Public Methods
 
     public override func viewDidLoad() {
         super.viewDidLoad()
         setupUI()
+        setupDataSource()
         bindViewModel()
         viewModel.fetchEmployees()
     }
     
     // MARK: - Private Methods
     
+    
+    /// Setting up the TableView Datasource
+    private func setupDataSource() {
+        dataSource = UITableViewDiffableDataSource<Int, Employee>(tableView: tableView) { tableView, indexPath, employee in
+            guard let cell = tableView.dequeueReusableCell(withIdentifier: EmployeeTableViewCell.identifier,for: indexPath) as? EmployeeTableViewCell else {
+                return UITableViewCell()
+            }
+            cell.configure(with: EmployeeCellViewModel(employee: employee))
+            return cell
+        }
+    }
+    
+    //Snapshot Handling
+    private func applySnapshot(employees: [Employee]) {
+        var snapshot = NSDiffableDataSourceSnapshot<Int, Employee>()
+        snapshot.appendSections([0])
+        snapshot.appendItems(employees, toSection: 0)
+        dataSource.apply(snapshot, animatingDifferences: true)
+    }
+    
     /// Setup the UI by adding the views to the main view
     private func setupUI() {
         view.backgroundColor = .white
         
         // Configure TableView
         tableView.register(EmployeeTableViewCell.self, forCellReuseIdentifier: EmployeeTableViewCell.identifier)
-        tableView.dataSource = self
         tableView.delegate = self
         view.addSubview(tableView)
         tableView.frame = view.bounds
@@ -109,9 +131,8 @@ class EmployeesViewController: UIViewController {
     private func bindViewModel() {
         viewModel.$employees
             .receive(on: RunLoop.main)
-            .sink { [weak self] _ in
-                self?.updateFooter()
-                self?.tableView.reloadData()
+            .sink { [weak self] employees in
+                self?.applySnapshot(employees: employees)
             }
             .store(in: &cancellables)
         
@@ -135,6 +156,26 @@ class EmployeesViewController: UIViewController {
             .store(in: &cancellables)
     }
     
+    private func animateEmployeeChanges(from oldEmployees: [Employee], to newEmployees: [Employee]) {
+        let oldCount = oldEmployees.count
+        let newCount = newEmployees.count
+
+        // Case: Removing all employees
+        if oldCount > 0 && newCount == 0 {
+            let indexPaths = (0..<oldCount).map { IndexPath(row: $0, section: 0) }
+            tableView.performBatchUpdates {
+                tableView.deleteRows(at: indexPaths, with: .fade)
+            }
+            return
+        }
+
+        // Case: Resetting with new data (or switching modes)
+        if newCount > 0 {
+            tableView.reloadData()
+            return
+        }
+    }
+    
     /// Show state in specific use-cases for the EmployeesViewModel
     private func updateFooter() {
         var footerMessage: String?
@@ -212,19 +253,3 @@ extension EmployeesViewController {
         viewModel.changeMode(to: selectedMode)
     }
 }
-
-/// Mark: - UITableViewDataSource
-extension EmployeesViewController: UITableViewDataSource {
-    public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
-        return viewModel.employees.count
-    }
-    
-    public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
-        guard let cell = tableView.dequeueReusableCell(withIdentifier: EmployeeTableViewCell.identifier, for: indexPath) as? EmployeeTableViewCell else {
-            return UITableViewCell()
-        }
-        let employee = viewModel.employees[indexPath.row]
-        cell.configure(with: EmployeeCellViewModel(employee: employee))
-        return cell
-    }
-}

EmployeeDirectory/ViewModels/EmployeesViewModel.swift

@@ -13,7 +13,7 @@ import Combine
 @MainActor
 public class EmployeesViewModel: ObservableObject {
     private var serviceMode: EmployeeServiceMode = .production
-    private var employeeService: EmployeeServiceProtocol = EmployeeService.shared
+    private var employeeService: EmployeeServiceProtocol = MockEmployeeService.shared
     @Published public private(set) var employees: [Employee] = []
     @Published public private(set) var errorMessage: String? = nil
     @Published public private(set) var isLoading: Bool = false
@@ -34,6 +34,7 @@ public class EmployeesViewModel: ObservableObject {
     /// Observe changes to sortField and sortOrder and debounce fetch calls
     private func observeSortingChanges() {
         Publishers.CombineLatest($sortField, $sortOrder)
+            .dropFirst()
             .debounce(for: .milliseconds(300), scheduler: DispatchQueue.main)
             .sink { [weak self] _, _ in
                 self?.resetAndFetchEmployees()
@@ -55,16 +56,16 @@ public class EmployeesViewModel: ObservableObject {
                                                                      sortField: sortField,
                                                                      sortOrder: sortOrder)
                 
+                totalEmployees = wrapper.total
+                currentPage = page
+                hasMorePages = wrapper.employees.count < totalEmployees
+                
                 // Update published properties
                 if page == 1 {
                     employees = wrapper.employees // Replace list for the first page
                 } else {
                     employees.append(contentsOf: wrapper.employees) // Append for subsequent pages
                 }
-                
-                totalEmployees = wrapper.total
-                currentPage = page
-                hasMorePages = employees.count < totalEmployees
             } catch {
                 // Handle errors
                 errorMessage = "An unexpected error occurred, please try to refresh."