What is the Coordinator Pattern?

Project Structure

CoordinatorExample/├── Coordinators/│   ├── MainCoordinator.swift          # Main tab navigation coordinator│   ├── LocationsCoordinator.swift     # Locations tab coordinator│   └── AccountCoordinator.swift       # Child coordinator for account flow├── ViewControllers/│   ├── TabBarViewController.swift     # Tab bar setup and coordinator management│   ├── MainViewController.swift       # Main tab content│   ├── LocationsViewController.swift  # Locations tab content│   ├── AccountViewController.swift    # Account screen (managed by child coordinator)│   ├── DetailViewController.swift     # Simple detail screen│   └── BottomSheetViewController.swift # Example modal presentation├── Models/│   └── User.swift                     # Example data model├── AppDelegate.swift└── SceneDelegate.swift               # App entry point

Key Features Demonstrated

✅ Tab Bar with Coordinators

✅ Child Coordinators

✅ Data Passing

✅ Multiple Navigation Types

✅ Navigation Bar Customization

Architecture Overview

TabBarViewController├── MainCoordinator (Tab 1)│   ├── MainViewController│   ├── DetailViewController│   ├── BottomSheetViewController (modal)│   └── AccountCoordinator (child)│       └── AccountViewController└── LocationsCoordinator (Tab 2)    └── LocationsViewController

How It Works

1. App Launch & Tab Setup

// SceneDelegate creates the tab bar controllerwindow?.rootViewController=TabBarViewController()// TabBarViewController sets up coordinators for each tabclassTabBarViewController:UITabBarController{privatevarmainCoordinator:MainCoordinator?privatevarlocationsCoordinator:LocationsCoordinator?overridefunc viewDidLoad(){letmainNavController=UINavigationController()letlocationNavController=UINavigationController()                mainCoordinator=MainCoordinator(navigationController: mainNavController)        locationsCoordinator=LocationsCoordinator(navigationController: locationNavController)                // Configure tab items and start coordinators}}

2. Tab-Specific Navigation

// Each tab has its own coordinator managing its navigation stackclassMainCoordinator:NSObject,Coordinator,UINavigationControllerDelegate{func start(){letvc=MainViewController()        vc.mainCoordinator=self        vc.title="Main VC"        navigationController.pushViewController(vc, animated:false)}func showDetailViewController(){letvc=DetailViewController()        vc.mainCoordinator=self        vc.title="Some Detail VC"        navigationController.pushViewController(vc, animated:true)}}

3. Child Coordinator with Data

// Complex flows use child coordinatorsfunc showAccount(){letcurrentUser=getCurrentUser()letchild=AccountCoordinator(navigationController: navigationController)    child.parentCoordinator=self    childCoordinators.append(child)    child.start(user: currentUser)}

4. Automatic Memory Management

// Coordinators automatically clean up child coordinators when users navigate backfunc navigationController(_ navigationController:UINavigationController, didShow viewController:UIViewController, animated:Bool){    // Detect back navigation and cleanup child coordinatorsiflet accountViewController= fromViewControlleras?AccountViewController{childDidFinish(accountViewController.accountCoordinator)}}

Key Classes

Coordinator Protocol

protocolCoordinator:AnyObject{varchildCoordinators:[Coordinator]{getset}varnavigationController:UINavigationController{getset}}

TabBarViewController

MainCoordinator

LocationsCoordinator

AccountCoordinator

Navigation Examples

Push Navigation

func showDetailViewController(){letvc=DetailViewController()    vc.mainCoordinator=self    vc.title="Some Detail VC"    navigationController.pushViewController(vc, animated:true)}

Modal Presentation (Bottom Sheet)

func presentSomeBottomSheet(){letbottomSheetViewController=BottomSheetViewController()    bottomSheetViewController.mainCoordinator=self    bottomSheetViewController.modalPresentationStyle=.pageSheetiflet sheet= bottomSheetViewController.sheetPresentationController{        sheet.detents=[.medium(),.large()]        sheet.preferredCornerRadius=16        sheet.prefersGrabberVisible=true}        navigationController.present(bottomSheetViewController, animated:true)}

Child Coordinator with Data Injection

func showAccount(){letcurrentUser=getCurrentUser()letchild=AccountCoordinator(navigationController: navigationController)    child.parentCoordinator=self    childCoordinators.append(child)    child.start(user: currentUser)}// In AccountCoordinatorfunc start(user:User){letvc=AccountViewController(user: user)    vc.accountCoordinator=self    vc.title= user.name    navigationController.pushViewController(vc, animated:true)}

Memory Management

// TabBarViewController keeps coordinators aliveprivatevarmainCoordinator:MainCoordinator?privatevarlocationsCoordinator:LocationsCoordinator?// View controllers hold weak referencesweakvarmainCoordinator:MainCoordinator?weakvaraccountCoordinator:AccountCoordinator?

Data Models

User Model

structUser:Codable,Identifiable{private(set)varid=UUID()letname:Stringletemail:Stringletage:Int}

Best Practices Demonstrated

Running the Project

Requirements

Navigation Flows

Main Tab Flow

MainViewController├── DetailViewController (push)├── BottomSheetViewController (modal)└── AccountCoordinator    └── AccountViewController (with User data)

Locations Tab Flow

LocationsViewController└── (Additional location-specific navigation can be added)

Benefits Over Traditional Navigation

Extension Ideas