iOS Developer: Must-Ask Interview Questions

Prepping to interview a candidate for your iOS Developer position, but unsure of what questions to ask to ensure you’re finding someone who can bring that “extra something” to your company? We’ve got what you need. Use these sample questions to help you determine which iOS Developer candidate is more than merely skilled and experienced in the basics—someone who will bring the acumen that can help elevate your company and support its needs above and beyond the usual. Not only will that help make the interview process easier, it will also help you uncover the tech professionals who are deep-thinkers, high-performers, and all-around true standouts.



Question: How would you avoid retain cycles when using closures/blocks in Swift?

Why you should ask: This is an important question because it helps uncover whether a developer has a clear understanding of retain cycle, and how to avoid it. That’s must-have knowledge for every iOS Developer, even though Apple greatly improved memory management with the introduction of ARC.

An answer you’d hear from a standout candidate: Closures can cause retain cycles because they have a strong reference to the object that uses them. (Note: A really solid answer from an iOS Developer should also mention the use of “[unowned self]” or “[weak self].”)


Question: What long-running tasks can iOS support in the background?

Why you should ask: Among all interview questions you might ask an iOS Developer, this one is particularly crucial. It helps reveal whether a developer has worked on, or at least experimented with a, broad range of iOS functionality. Mobile clients regularly ask for functionality that iOS doesn’t provide and developers need to understand the limits of the operating system.

An answer you’d hear from a standout candidate: There are several background tasks, including location services, Bluetooth Low Energy (BLE) and audio playback. Would you like me to share some examples of how I’ve worked with some of this functionality?


Question: When would you use a third-party library or Software Development Kit (SDK) it in your development?

Why you should ask: Many iOS Developer candidates will tell you that a third-party library or SDK can speed up development. But you want a potential hire for an iOS Developer role to provide a more thoughtful response. Here’s why: As new iOS versions and devices are released, maintaining applications in the medium- to long-term becomes challenging. Adding a third-party library, and its attendant features, which will cease to be supported, can create even more problems.

An answer you’d hear from a standout candidate: I use them sparingly when I feel that the library has a long history, is current, well-supported and exceeds the functionality that is required.