Screen Navigation in iOS
Article Summary
Bohdan Orlov tackles one of iOS development's messiest problems: screen navigation that's actually testable and maintainable. Most apps get this wrong from day one.
This deep dive walks through iOS navigation patterns from basic UIViewController presentations to sophisticated coordinator architectures. Orlov progressively adds abstraction layers to decouple screens and make navigation logic unit testable, addressing real-world challenges like deep links and push notifications.
Key Takeaways
- Storyboard segues force runtime string identifiers and two-step initialization patterns
- Protocol-oriented dependency injection decouples view controllers and enables unit testing
- Flow Coordinators create module facades but require parallel UI hierarchy maintenance
- Deep link navigation uses graph algorithms to reconcile actual vs required screen stacks
- Priority-based modal handling prevents blocking screens from breaking navigation flows
Moving from coupled UIViewController presentations to testable, protocol-based navigation requires strategic abstraction layers that balance flexibility with architectural complexity.
About This Article
iOS view controllers often have tight coupling that makes navigation logic hard to unit test. OCMock and swizzling are common workarounds, but they don't work well with pure Swift classes.
Bohdan Orlov's team used presenter and view controller factory closures injected through protocols like ViewControllerPresenting. This let them create mock implementations for isolated unit testing without modifying UIViewController internals.
Developers can now verify navigation decisions in unit tests by checking what arguments were passed to mock presenters. This catches bugs like string identifier typos in storyboards and XIBs before they cause runtime crashes.