iOS Developer Interview Questions

BrainStation’s iOS Developer career guide is intended to help you take the first steps toward a lucrative career in iOS development. Read on for some common iOS Developer job interview questions, as well as strategies on how to answer them.

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The interview process for an iOS Developer position will test your programming skills, iOS knowledge, and how well you would fit in with the company. iOS Developer interviews can vary—some may ask lots of detailed technical questions, while others may focus on your experiences so far. You may also be asked to do a whiteboard interview or take-home assignment that tests your iOS development skills.

To ace the interview, you should brush up on your development knowledge, practice your skills, and review your previous experiences and accomplishments. Here are a few tips to keep in mind:

  • Read through the company’s website and download their apps
  • Practice common interview questions out loud
  • Practice coding on a whiteboard
  • Remember to articulate your thought process – this is more important than arriving at the right answer
  • Ask the interviewer clarifying questions as needed

To help you prepare for the range of questions that may come up in your interview, we have put together a list of commonly asked iOS Developer interview questions.

iOS Developer Interview Questions: iOS Development

The first set of iOS interview questions you may encounter are questions that test your development knowledge. Employers will be looking to see if iOS Developers have a thorough understanding of Objective-C and Swift, as well as iOS standards and best practices.

A few examples of iOS interview questions and answers are:

How proficient are you in Objective-C and Swift? Can you briefly describe their differences?

First of all, an iOS Developer should be deeply familiar with both Objective-C and Swift, the two programming languages used for iOS and Apple products. Objective-C was created in the mid-1980s as an extension of C, and its interoperability with C++ remains one of its biggest draws. Apple created Swift in 2014 specifically for developing software on its operating systems. Since Swift was developed using three decades of Objective-C experience, it’s an improvement in many ways. Swift is open-source, easier to learn, offers interactive development using Playgrounds, offers support for namespaces and concise syntax, and – unlike Objective-C – it can be used with Cocoa Touch to develop Apple TV or Apple Watch apps. But you should also stress that you don’t have to choose – Apple has made Objective-C and Swift interoperable and many companies use both in their apps.

What is the difference between not-running, inactive, active, background, and suspended execution states?

Here’s a simple way to explain the different iOS application states to answer this interview question:

  • What are the main features and advantages or disadvantages of Swift?
  • How is memory management handled on iOS?
  • What is MVC?
  • What design patterns are commonly used in iOS apps?
  • What options do you have for implementing storage and persistence on iOS?
  • What are the options for laying out UI on iOS?
  • What iOS architectures do you know that scale?
  • What’s the difference between atomic and nonatomic synthesized properties?
  • What iOS frameworks do you have experience working with?
  • What are Key-Value Coding and Key-Value Observing?
  • Can you explain how iOS supports multi-threading?
  • What is managed object context and what is its functionality?
  • Name four important data types found in Objective-C.
  • What are user interface elements and some common ways you can add them to your app?
  • What are some common execution states in iOS?
  • Explain the difference between raw and associated values in Swift.
  • What security best practices do you know?

iOS Developer Interview Questions: Technical Skills

You will need to put your skills on display in an interview for an iOS Developer job. Expect employers to ask technical questions that assess whether you can excel at the job. These may be given in the form of a whiteboard challenge or take-home assignment. Remember to ask questions if there is any ambiguity and to thoroughly and clearly explain your thought process.

Examples of technical skills interview questions are:

What’s the difference between synchronous and asynchronous tasks within iOS?

You can expect some quiz-like reference questions in this section of the interview – these have less to do with your particular methods and more to do with providing you have the knowledge that all successful iOS developers need to know. Don’t worry if your answers to questions like this are short and to the point. Here, you can explain that synchronous tasks depend on previous tasks being finished before proceeding, while asynchronous tasks can all function at the same time in the background.

  • What interfaces would you choose to create a user-friendly application?
  • How do you optimize scrolling performance of dynamically sized table or collection views?
  • How do you execute asynchronous tasks on iOS?
  • How do you debug and profile code on iOS applications?
  • Explain your process for tracing and fixing memory leaks.
  • In C, how would you reverse a string as quickly as possible?
  • Explain the purpose of the reuse Identifier in the UITableViewCell constructor.
  • Determine the value of “x” in the Swift code below. Explain your answer.
  • Find the bug in the Objective-C code below. Explain your answer.
  • You’ve just been alerted that your new app is prone to crashing. What do you do?
  • What are KVC and KVO? Give an example of using KVC to set a value.
  • How would you securely store private user data offline on a device? What other security best practices should be taken?
  • How would you convert the codebase of an existing iPhone or iPad app?
  • How would you go about structuring an iOS application that you are building from the ground up?

iOS Developer Interview Questions: Personal

Technical skills and expertise are necessary for all iOS Developers, but employers are also looking for the right personality and attitude. Personal questions assess whether you would be a good team member and how well you would fit into the company culture.

A few examples of personal questions are:

Why did you choose to specialize in iOS Development?

This is a personal question and each applicant will have a different answer. A practical response might point to the ubiquity of Apple’s products, as well as the increasing importance of developing products with a mobile-first mindset. It would also be valid to point to your passion for Apple’s products, design and clean interface, and relatively user-friendly security policies.

  • Which of the applications you designed are you most proud of?
  • What’s your area of expertise and what would you like to learn about more?
  • What was the last thing you read in a book or blog that you find helpful for your work?
  • What are some of your strengths and weaknesses?
  • Can you describe yourself in three to five words?
  • Do you work better alone or as part of a team?
  • Where do you see yourself in five years?
  • If you were an animal, which one would you want to be?
  • How do you handle stressful situations?
  • Tell me about yourself.
  • Do you work better under pressure or with time to plan and organize?
  • What is more important: completing a job on time or doing it right?
  • Why do you consider this to be a good opportunity for you?
  • Describe your impact on your present company.
  • Why do you want to work here?
  • What technical projects have you contributed to (e.g. open-source projects) outside of work and/or school?
  • What publications, websites, blogs and communities do you follow?
  • What is your favorite iOS application?

iOS Developer Interview Questions: Leadership and Communication

To see if you have the skills needed to lead a team or project and articulate your development process, expect interview questions such as:

Provide an example of a time when you didn’t agree with other programmers. Did you stand up for something that you believed was right?

Something like this question should be expected in all kinds of jobs, not just within development, and your strategy for answering it should be similar. When you give the example, clearly lay out the situation and the goals of your team. Make sure to express an understanding of the motivation of the other developers. Even as you explain why your methods might have been ultimately proven right, be humble, and show how you ultimately gathered buy-in from the other team members.

  • Tell me about a time when you had to present a complex programming problem to a person who didn’t understand technical jargon. How did you ensure that the other person understood you?
  • Describe a situation in which you felt you had not communicated well. What did you do? How did you handle it?
  • Tell me about a situation where you had to speak up and be assertive in order to get a point across.
  • Tell me about the most difficult situation you had when leading a team. What happened and how did you handle it?
  • Have you ever had to “sell” an idea to your project team? How did you do it? Did they “buy” it?

iOS Developer Interview Questions: Behavioral

Behavioral interview questions require you to recall a time you displayed certain hard and soft skills. For these types of questions, discuss a specific situation, what you did in the situation, and the outcomes you achieved. Emphasize what you learned from the experience.

Examples of behavioral interview questions are:

Describe a time when you collaborated with engineers and designers for a group project. What was your role?

Few developers work in isolation. Interviewers will want to make sure that you’re a team player who can take direction and work in close collaboration with any number of professionals – including those with and without a technical background. If the technical questions are an opportunity for you to show off your ability, this is your chance to talk about how bringing together different skillsets and areas of expertise on a big project ultimately worked to the benefit of all involved. Be sure to emphasize the collaboration aspect and go into detail on any other stakeholders who might have been involved.

  • Describe a time when you collaborated with engineers and designers for a group project. What was your role?
  • Describe a time when you designed new features to make an application run faster.
  • Describe a time when you made a suggestion to improve something on the project that you were working on.
  • Has there been a time on a project when you disagreed with someone? What did you do about it?
  • Give me an example of a time you had to take a creative and unusual approach to solve a coding problem.
  • Describe a situation in which you worked diligently on a project and it did not produce * the desired results. Why didn’t you get the desired results? What did you learn from the experience?
  • Think about an instance in which you had to depend on others to help you achieve a project goal. How did you feel?
  • Tell me about a situation when you made a mistake at work. What happened and how did you deal with it? What steps did you take to improve the situation?
  • Describe a team experience you found disappointing. What would you have done differently to prevent this?
  • Describe an interesting problem and how you solved it.

iOS Developer Interview Questions From Top Companies (Amazon, Google, Facebook, Microsoft)

To give you an idea of the skills and expertise top tech companies are looking for in an iOS Developer, here are a few interview questions from Amazon, Google, Facebook, and Microsoft.

  • Develop a small feature in Objective-C.
  • What type of leader do you prefer to work for?
  • Design a photo stream app.
  • What is your least favorite Cocoa API?
  • Write a method to compare two binary trees.
  • What is the most challenging task you ever had?
  • How does memory management work on iOS?
  • How would you implement UIView hitTest method?
  • Find the path between two nodes of a tree.
  • Design a library to trace the code execution flow.
  • Implement a hash map data structure.