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Explain the Coordinator Pattern and Its Benefits

· 2 min read
Szymon Michalak
Szymon Michalak
iOS Developer
Sources & Resources

Main Source: đź”— Coordinator Pattern in iOS

Additional Sources:

Further Reading:

TL/DR

The Coordinator pattern is a design pattern in iOS development that helps manage navigation flow and dependency between view controllers, leading to better-organized, more modular, and testable code.

The Coordinator pattern is an architectural pattern used in iOS development to manage the flow of navigation within an application. Instead of letting view controllers handle the navigation, a separate coordinator object takes over this responsibility. This leads to a more organized structure where view controllers are only responsible for displaying content, and the coordinator handles the logic of navigating between screens.

Code Examples​

Here's a basic example of implementing the Coordinator pattern in Swift:

protocol Coordinator {
    var childCoordinators: [Coordinator] { get set }
    func start()
}

class MainCoordinator: Coordinator {
    var childCoordinators = [Coordinator]()
    var navigationController: UINavigationController

    init(navigationController: UINavigationController) {
        self.navigationController = navigationController
    }

    func start() {
        let vc = ViewController()
        vc.coordinator = self
        navigationController.pushViewController(vc, animated: true)
    }

    func showDetail() {
        let detailVC = DetailViewController()
        detailVC.coordinator = self
        navigationController.pushViewController(detailVC, animated: true)
    }
}

In this example, MainCoordinator is responsible for initializing the first view controller and handling the navigation logic for showing a detail view controller.

Real-World Applications​

The Coordinator pattern is particularly beneficial in large-scale applications where complex navigation flows exist. By separating the navigation logic from view controllers, the code becomes easier to manage, test, and maintain. It also promotes reusability, as the same coordinator can handle similar navigation flows across different parts of the app.

Common Mistakes​

  • Tight Coupling: One common mistake when implementing the Coordinator pattern is allowing coordinators to become tightly coupled with specific view controllers, reducing flexibility.
  • Overcomplication: Sometimes, developers overcomplicate the Coordinator pattern by creating too many coordinators for simple flows, leading to unnecessary complexity.
In Bullets
  • Decouples Navigation from View Controllers: By moving navigation logic out of view controllers, the Coordinator pattern promotes cleaner and more modular code.
  • Improves Testability: Coordinators can be easily tested in isolation, leading to better test coverage for navigation logic.
  • Enhances Reusability: Coordinators can be reused across different parts of an application, especially in complex flows.