Why do new bugs keep appearing in your iOS app? As an experienced iOS developer, I've encountered this issue numerous times. It's not just about being careless; there are underlying reasons that can be addressed with the right approach.
Architecture is the Foundation
The key to building a bug-free iOS app lies in its architecture. Many projects struggle with technical difficulties that stem from architectural decisions made at the beginning of the project. A well-designed architecture ensures that each component has a clear role, making it easier to test and maintain. On the other hand, an organic architecture can lead to massive View Controllers and mixed code, resulting in unforeseen effects and bugs.
The Five Main Causes of Bugs
I've identified five main causes of bugs in iOS apps:
Lack of Clear Separation of Responsibilities
When a single class handles multiple responsibilities, testing becomes a nightmare. This is where the Single Responsibility Principle comes into play, drastically reducing the scope of potential bugs.
Poor State Management
State is everything in mobile apps. When the same piece of information lives in three different places and is synchronized manually, it's only a matter of time before those places start contradicting each other.
Tight Coupling with Frameworks and External Dependencies
When business logic is intertwined with UIKit, CoreData, or specific networking libraries, every framework change becomes open-heart surgery. Testing such code is extremely difficult, leading to the abandonment of unit testing.
Lack of Error Handling Strategy
Throughout my career, I've seen code where errors are simply ignored or inadequately handled. This can lead to unexpected crashes and a poor user experience.
Ignoring the Application Lifecycle
iOS has specific requirements regarding the lifecycle of applications and view controllers. Code that doesn't account for these scenarios works great on the developer's device but falls apart for users.
What You Can Do to Avoid Bugs
To avoid bugs and improve your app user experience, follow these best practices:
Invest Time in Architecture Upfront
Consciously design your architecture to ensure a clear separation of responsibilities and make it easier to test and maintain. This investment will save you weeks of debugging later.
Apply Dependency Injection Consistently
Use dependency injection to test components in isolation and swap implementations without rewriting half the app.
Treat Errors as a Priority
Every operation that can fail should have an explicitly modeled error path. Swift gives us great tools for this, such as Result, throws, and async/await with error handling.
Model States Explicitly
Use enums and associated values to model states explicitly, making it easier to catch bugs before the code reaches a device.
Write Tests for Business Logic
Test those places where decisions are actually made. If your architecture doesn't let you write such tests without mocking half the iOS SDK, that's a sign something's wrong with the architecture.
Take Code Review Seriously - Both Ways
Code review isn't just about checking off boxes or finding typos. It's a moment when a second pair of eyes can catch logic errors that you missed. Learn from reviews and use them to improve your code.
Use AI as Your First Line of Defense
Tools like GitHub Copilot or Claude can catch potential problems before code even reaches review. An unhandled optional, a missing case in a switch, or a race condition - AI is getting better at recognizing these patterns.
By following these best practices and prioritizing app user experience, you can create an iOS app that provides a seamless and enjoyable experience for your users.