As a seasoned mobile app developer, I've often found myself scratching my head when dealing with pesky bugs in our iOS apps. Why do new issues keep popping up after we fix one? Is it simply the result of careless coding, or is there something more at play?
The Foundation of Bug-Free Development: Architecture
It turns out that many problems don't stem from technical difficulties, but rather from architectural decisions made (or not made) at the beginning of a project. In other words, the way we design our apps can either lead to a sea of bugs or a bug-free paradise.
The Top 5 Causes of Bugs in iOS Apps
As I've seen firsthand, a lack of clear separation of responsibilities, poor state management, tight coupling with frameworks and external dependencies, inadequate error handling strategies, and ignoring the application lifecycle can all contribute to a bug-prone app. Let's dive into each of these common pitfalls:
Lack of Clear Separation of Responsibilities
When one class handles data fetching, transformation, validation, caching, and presentation, testing becomes a nightmare, and every modification is a risk. By following the Single Responsibility Principle, we can drastically reduce the scope of potential bugs.
Poor State Management
In mobile apps, state is everything - view state, user session state, network connection state, cache state. When information lives in multiple 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 a specific networking library, every framework change becomes open-heart surgery. Testing such code is extremely difficult, which leads most teams to simply give up on unit testing.
Lack of Error Handling Strategy
Throughout my career, I've often seen code where errors are simply ignored or inadequately handled: empty catch blocks, ignored Result.failure, optionals force-unwrapped "because there's always something there." And then an edge case no one anticipated comes along, and the app crashes with no information about why.
Ignoring the Application Lifecycle
iOS has specific requirements regarding the lifecycle of applications and view controllers. An app can be suspended, resumed, or killed in the background. A view can be deallocated and recreated. Code that doesn't account for these scenarios works great on the developer's device and falls apart for users.
The Solution: Building a Bug-Free iOS App
So, what can we do to avoid bugs and make our lives easier? Here are some actionable tips:
Invest Time in Architecture Upfront
Consciously thinking through how information will flow in the app, where business logic will live, and how modules will communicate can save weeks of debugging later.
Apply Dependency Injection Consistently
This practical tool allows us 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 - Result, throws, async/await with error handling. Let's use them instead of pretending errors don't exist.
Model States Explicitly
Instead of five scattered booleans, use an enum with associated values. Instead of optional fields that "are always filled after login," create separate types for logged-in and logged-out users.
Write Tests for Business Logic
I'm not talking about 100% code coverage - I'm talking about covering with tests those places where decisions are actually made.
Take Code Review Seriously - Both Ways
Code review isn't a formality to check off or a hunt for typos. It's the moment when a second pair of eyes can catch a logic error that you missed after several hours of sitting in the same 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, a race condition when accessing shared state - AI is getting better at recognizing these patterns.
Document Your Decisions, Not Just Your Code
Code tells you how something should be done, but documentation helps others understand why it was done that way.