Describe the most complex problem with an error you have dealt with and how you solved it.

One of the challenging problems I faced was related to memory leaks caused by cyclic references in Swift. In one project, the app unexpectedly started to slow down significantly and consume a lot of memory.

I used Xcode tools — Instruments with the Allocations and Leaks profilers to track down where exactly the leak was happening. It turned out that in several places, closures captured self without using weak references ([weak self]), which led to cyclic references and prevented objects from being deallocated.

Solution:

• Wherever closures used self, I added [weak self] or [unowned self] depending on the context.
• I rechecked the lifecycle of objects and ensured they were properly released.
• After making these changes, I retested the app using Instruments — no leaks were found, and performance returned to normal.