Top iOS Interview Questions and Answers

Are you trying to hire an iOS Developer to build a stellar iOS App for your company? iOS technology is continuously updating and sometime it can be challenging for recruiters/hiring manager to ask the right questions from the candidates.  Interview process begins with the recruiter, where the recruiter will ask basic screening questions to make sure the candidate is fit for the next round of technical interview. We have created a comprehensive list of questions that Recruiters and Technical Managers can ask for interviewing an iOS Developer. These questions will help you with both kinds of interviews Face-to-face interviews and video interview.

Initial Screening Questions to be asked by Recruiters

Q1: How many years have you worked in iOS Development?

Candidates should be able to tell the number of years spent on iOS development. If a candidate’s experience is 1-2 years, the candidate is at junior level. 2-5 years experience is mid level, 5+ years experience in Senior level.

Q2. How many apps have you published in the app store?

Candidates should be able to tell how many apps are published in the app store. A junior level candidate should have published at least 1-2 apps on the app store. Mid level iOS developers should have published 2-5 apps, a Senior level candidate should have published 5+ apps.

Q3. What database have you used in building an iOS App?

CoreData is used to save data locally in the app. Backend database could be MySQL, MongoDB, NoSQL, AWS-DynamoDB.

Q4. What experience do you have in integrating APIs with the app?

Candidate should be able to tell the recruiters about the exp in integrating APIs with the app.

Q5. Have you worked on third party APIs?

Candidate should be able to tell you if he/she has worked on integrating third party APIs in the app like Facebook API, Instagram API, Paypal API.

Q6. How would you create the user interface of the app:

User interface is created using storyboards, XIBs.

Q7. What tools do you use to test the performance of your app?

Instruments, Accessibility Inspector

Q8. What is ARC?

ARC (Automatic Reference Counting) is a memory and object lifetime management model of Elements compiler that manages object life cycles. It tracks all valid references to an object via an internal retain count.

Q9. Define Bundle ID?

The bundle ID or identifier is used to identify an update in your app. It is used in both iOS and OS X apps.

Q10. What are the data types found in objective C?

There are four data types in objective-C: Bool, NSintegar, CGfloat, and string.

Q11. Define Cocoa/Cocoa touch?

Cocoa touch in an Object-C language used for developing software codes. It comprises a unique set of graphical control elements and runs only on iOS.

Q12. What are programming languages used for iOS development?

Programming languages used for iOS development are:

  • Swift
  • Objective-C

Q13. What are the methods required for concurrency?

The processes for concurrency are

  • Dispatch queues
  • Threads
  • Operation Queues

Q14. What is the difference between atomic and non-atomic synthesized properties?


    • Default behavior
    • Not fast
    • Make sure the CPU completes the process


      • Not default behavior
      • Faster
      • It can deal with multiple requests simultaneously

Q15. How would you know when an app is not running the state?

An app that fails while launching or gets terminated by the system when put to execution.

Q16. What is an object?

Objects are instances of a class and contain states and behavior. For example, if a dog is an object, its states are colors, names, and breed. Similarly, its behavior is barking, eating, and wagging its tail.
In software development, fields store a software object, and its behavior is displayed through methods.
Objects can be a function, data structure, variable, or method.

Q17. How to know if an app is in an active state?

An app that accepts events and runs in the foreground is considered to be in its active state.

Q18. What framework is required to develop an application’s user interface?

UIKIT framework. It renders drawing models, windows, event handling, and views.

Q19. What is iBeacon?

iBeacon is a system that empowers mobile apps to receive and respond to signals from beacons from the real world. It comes with a broadcaster and a receiver.

Q20. Define Method Swizzling?

Method Swizzling is a process that involves swapping or exchanging implementation of two runtime methods and modifying the behavior of framework classes. It is mostly used to implement complex functions with ease.

Q21. Define Method Swizzling?

Method Swizzling is a process that involves swapping or exchanging implementation of two runtime methods and modifying the behavior of framework classes. It is mostly used to implement complex functions with ease.

Q22. When is the category used?


  • It is called when data is loaded into memory.
  • Data that are static and are likely to change can be loaded in Viewdidload.


  • It is called when the view is visible and presented on the device.
  • It allows you to perform any layout functions or draw in the UI.


Q23. What does KVO stand for?

KVO means key-value observing through which a controller can observe changes to property value.

Q24. What is GCD?

GCD (Grand Central Dispatch) is a library that enables object-based and low-level APIs to run tasks accordingly while managing threads.

Q25. Which method is used for executing final utilization before presenting the app to the end-user?

Before presenting the app to the user, we can use “application:didFinishLaunchingWithOptions” to execute the code for the first time.

Q26. What is Code Coverage?

Code coverage is used to estimate the unit tests values.

Q27. What is a Responder Chain?

A Responder Chain is the hierarchy of objects that can respond to events received.

Q28. What is Operator Overloading?

Operator overloading is used to work on how existing operators perform with types that already exist. Operators are those little symbols like +, *, and /.

Q29. What is the role of design patterns in Linux?

Design patterns consist of different templates used to solve common software design problems. It is used to write easy-to-understand codes.

Some common Cocoa design patterns include:

  • Creational: Singleton.
  • Behavioral: Observer, and, Memento
  • Structural: Decorator, Adapter, Facade


Q30. Explain the Adapter Pattern?

An adapter can integrate with classes with adverse interfaces putting it in sync. It also integrates with an object and allows it to interact with a standard interface.

Q31. Explain the Observer Pattern?

The observer pattern is a design pattern with one too many relations. It allows multiple objects (observer) to observe another Object (Subject) simultaneously. When one Subject changes its state, it is notified to the observers.
Cocoa uses the observer pattern in two ways:

  • Notifications
  • Key-Value Observing (KVO)


Q32. Name the APIs for battery-efficient location tracking?

Significant location changes: the location is delivered approximately every 500 meters (usually up to 1 km)

Region monitoring: track enter/exit events from circular regions with a radius equal to 100m or more. Region monitoring is the most precise API after GPS.

Visit events: monitor place Visit events which enter/exits from a place (home/office).

Q33. What is a delegate in swift?

Delegate is a design pattern, which is used to pass the data or communication between structs or classes. Delegate allows sending a message from one object to another object when a specific event happens and is used for handling table view and collection view events.

Q34. What is the difference between Array and NSArray?

The difference between Array and NSArray are given below:

  • An array can hold only one type of data, whereas NSArray can hold different types of data.
  • An array is a value type, whereas NSArray is an immutable reference type.


Q35. What is the difference between Upcast and Downcast in Swift?

  • The upcast, going from a derived class to a base class, can be checked at compile time and will never fail.
  • However, downcasts can fail since you can’t always be sure about the specific class. If you have a UIView, it’s possible it’s a UITableView or maybe a UIButton.


Q36. What does the Swift mutating keyword mean?

Being the value type, structs are immutable. Meaning other variables can not change the values for instance of structure at any given point.
The mutating word is required for changing the values of self variables inside the structure’s function only.

Q37. Can you add a stored property to a type by using an extension? How or why not?

No, it’s not possible. You can use an extension to add new behavior to an existing type, but not to alter either the type itself or its interface. If you add a stored property, you’d need extra memory to store the new value. An extension cannot manage such a task.

Q38. Are closures value or reference types?

Closures are reference types. If you assign a closure to a variable and copy the variable into another variable, you also copy a reference to the same closure and its capture list.

Recruiting in 2021

2020 saw the process of recruitment change drastically. The introduction of lockdown and curfew led to a dramatic shift in employee experience and recruitment strategies. Therefore, entering 2021, heads of the HR department will have to consider the following trends.

Remote working

It became popular in 2020. With most employees conducting their duties from their homes, last year was proof that running businesses remotely is possible. Although most companies will still retain the office, most human resource managers will create several remote working positions.

These positions will encourage flexibility in the workplace. Remote working will also attract the top talent since recruitments will not get limited to people within a commutable area.

Virtual recruitments

One of the biggest and most impactful changes in 2020 was implementing a virtual recruiting strategy. Virtual recruiting has proven to be effective and convenient for both the interviewers and the interviewee. Virtual recruiting became widespread due to the advantages it provided. These benefits include;

  • Time-saving
  • Freeing up resources
  • Allows HRs to interview a wider number of candidates
  • Allows a broader reach of candidates from all over the globe

This trend will soon become the norm in most businesses.

Diversity and Inclusion

Apart from the COVID19 pandemic, 2020 saw a significant cultural change where inclusion and diversity were at the forefront of the discussion. Therefore, progressing through 2021, heads of HR departments will need to focus on recruiting diverse candidates. They will also have to create new talent search strategies that will attract people of different diversity. Companies that fail to observe this trend will invite the risk of looking as if they do not care for inclusion. They will also appear as left behind and out of touch.

Use of AI and Automation

Another recruiting trend that will become apparent in 2021 is the use of Ai and Automation. The use of these Automations and AI systems will not replace the need for a recruiting team. These systems will help make the recruiting process easier and efficient. These Automated systems will offer the following services;

  • Candidate screening
  • Candidate-job marching
  • Job description and requirement screening
  • Automated conversations
  • Scheduling of interviews

The use of AI systems will increase efficiency and save time and reduce repetitive tasks.

Digital Attraction

With most people using social media platforms, the digital attraction will prove to be the secret towards talent search in 2021. Most human resource managers will use digital platforms to attract the most suitable candidates. They will also use platforms like Linkedin to evaluate the applying candidates.

How resume screening is changing the game for recruiters

Recruiters face high expectations. Their recruiting and onboarding goals rise every quarter, and their management does not always enable them with the tools they need to meet these higher expectations. Professionals who face these heightened expectations can’t just settle for human resources tips. They need the cutting edge of technology to facilitate their recruitment process. Today, that cutting edge is in resume screening technology.

Finding the Right Candidates

Resume screening software makes recruiters’ lives easier by taking some of their most time-consuming work out of the equation. It is easier than ever for applicants to respond to every job posting related to their work experience. That leaves recruiters the daunting task of sorting through hundreds of resumes of varying relevance. Resume screening software puts an initial filter on that huge applicant group and enables recruiters to spend more time looking at their best-qualified applicants. They need new tools to meet heightened goals.

The Ducknowl Difference

That’s why recruiters choose Ducknowl. With our powerful, AI-driven platform, we make sure human resources professionals we partner with have a clear view of their best-qualified applicants. Every day, recruiters use our customizable criteria and keyword weighting to create a focused pool of highly-qualified candidates to whom they can give individual attention. For many human resources departments, recruitment is a race against time. For our users, it is a simple, focused search for the best possible candidates.

Your Time is Valuable

Unfortunately, many people in search of simple human resources tips find programs that might be useful in theory, but are impractical in the fast-paced environment of a modern recruiter’s office. That is why it was so important to us that we build a platform that is as reliable as it is easy to use. After all, if you are looking for ways to save time, spending hours trying to learn new software starts to feel counterproductive. We value your time as much as you do, which is why our platform is so intuitive and user friendly.

Given how recruiters’ quotas rise every quarter, every human resources department interested in enabling their employees is on the hunt for the next powerful tool to make their team more efficient. Today, that tool is Ducknowl. We believe that the best resumes should get individual attention from recruiters. If you do too, find out firsthand just what we can do for you.

How DucknOwl can help in delivering a consistent employee experience?

No doubt, you invest considerably in your customer experience. And, you pay close attention to your customer satisfaction metrics. As an attentive owner or manager, you’ve likely come to the conclusion that your employee experience is the determining factor in what your customers experience. Whatever your employees believe your company is like, is — in an important way — exactly what your company is like. Your employees create your customer experience from their own beliefs about the firm.

Finding Ideal Tools to Improve Employee Experience

As your firm scales, you will need help with many of the internal moving parts. Third party services can help with everything from your recruitment process, to employee retention, and even ensuring smooth exits and off-boarding processes.

Eliminating Bias in Human Resources

We all have biases. As people, we can work incredibly hard to reduce and mitigate our problematic mental shortcuts. We need to recognize, though, that it is very hard just to be aware of all of our biases — let alone eliminate them. DucknOwl’s innovative solution provides data driven tools to ensure that your recruitment process is demonstrably free from bias. Strictly eliminating bias in hiring will create a work environment that your employees will recognize as fair and professional from their first day on the job. As they get to know their coworkers, they will find people different from them in all of the ways that will benefit the whole team, but well-qualified and similar to them in all of the ways that are critical to performance.

Make Candidates Feel Seen

Not every job is a copywriting position. It can be helpful to have more options to let job candidates present themselves than merely relying on the traditional resume. Give your prospective hires different options for demonstrating their capabilities and you will see them for who they are. They, in turn, will feel more valued, right from the start. DucknOwl allows you to accept audio files and collects and processes information in many more dynamic ways than you ever could by thumbing through a pile of resumes.

Respect Your Candidates’ Time

Consider your candidate’s situation. Looking for a job can include a lot of phone tag, complex scheduling problems, and — worst of all — waiting. Start your relationship off on the right foot by respecting your prospect’s time.

DucknOwl provides an innovative solution to make the screening and scheduling processes fast, so you’ll be getting back to the best contact fast. That also means that you’ll be getting to them before they’re snatched up by a competitor.

DucknOwl, helping the employer and the job seeker for the future

In the last year, the way all business has operated dramatically changed due to the effects of COVID-19. The nation has seen unemployment hit historically high levels due to the reduction and restructuring of business operations. The positive aspect of this current challenge is that at some point, it will end. When that time comes, there will be a need for companies to have efficient systems to identify and hire employees.

DucknOwl has developed a system for streamlining and increasing the efficiency of the employment process. Job seekers can go through a process of screening in their recruitment system that enhances their exposure. This system provides more organized information to the potential employer through multiple different outlets.

These outlets consist of resources like skill assessment, which measures soft skills with pre-recorded video interviews that you can share with your team. Multiple services, in conjunction with each other, make their system more effective than others. Using resume screening with the skill assessment alone can give you a productive edge in finding good employees. They also have audio screening being that we’re in the time of the pandemic. Many interviews are over the phone for people who may not have the capability to record a video. This system is another measure used to screen and select candidates for your job.

This system initially helps to invest time in the right candidate while filtering out irrelevant resumes and creating a candidate inventory. To humanize the hiring process, a hiring manager makes a job listing with weighted keywords, resulting in a ranked list of candidates in seconds. The system even has measures to eliminate unconscious bias by customizing video interview questions for a specific job or position.

DucknOwl has measures that prevent proxy interviews and bait-and-switch situations with identity verification of candidates. All processes follow EEO (Equal Employment Opportunity) compliance and SOC 2 for information security. Also, they are ADA (Americans with Disabilities Act) compliant. Meeting these requirements is an additional benefit to matching the right talent to the position.

Conscious or unconscious bias can be a counterproductive contribution to the workforce because you create a situation where you may be avoiding the people who are the best fit for the job reducing potential effectiveness.

The recruitment system is a catalyst to efficiently connecting job seekers with employers at a rate that can accommodate the future demand of the evolving job market for millions of Americans.

Video Interviews: Tips for Employers

The interviewing process includes several steps, including going through resumes, calling candidates, and conducting in-person interviews or skill assessments. Going through all these steps with multiple applicants takes a lot of time. Most of the time you are repeating the same steps with all shortlisted candidates. This is where a video interviewing process can be useful. Instead of calling 10 applicants and asking them the same questions, you can use video interviewing software to save time. We will be discussing different types of video interviews and their benefits:

What is Video Interviews?

Video interviewing consists of using online software to ask questions to applicants and record their answers for reviews and ratings. There are two common ways that most hiring managers conduct video interviews. First, there are recorded video interviewing platforms like Ducknowl, Sparkhire, and WePow. Second, there are live video calling systems like Zoom, Webex, and Skype. These videos can be conducted through one-way or two-way interviews:

One-Way Video Interviews

One-way video interviews involve sending the same pre-chosen questions to all candidates. Candidates receive the invitation and record their answers for each question. Typically, you can set a time limit for each question. For example, with Ducknowl, you can choose to limit the answer time for the candidate to two minutes for a specific question. Once candidates record their answers, recruiters will be notified of the interview completion. Afterward, they can view the responses at their convenience at a time of their choosing. They also will be able to share all responses with hiring managers and other members of their team for feedback.

Two-Way Video Interviews

A two-way video interview is a live interview using a video calling application such as Skype, Zoom, or Webex where the recruiter/hiring manager and candidate both join live. Interviewers come prepared with a list of questions as the candidate and may record the interview to review later or to share with other members of their team.

Benefits of Video Interviewing:

Reduce Time:
This is the biggest benefit when utilizing video interviews in your hiring process. It saves you time if you are using it to replace the phone interviews or in-person interviews. For phone interviews, recruiters spend a lot of time trying to coordinate a mutual time and date that works for them and their candidate, and often have to deal with last-minute scheduling conflicts. They spend time preparing and repeating the same questions with each candidate. For in-person interviews, the recruiter has to set aside time for each candidate’s visit. Not only does the interview itself take a substantial amount of time to conduct, but recruiters often dedicate extra time to make their experience pleasant by welcoming the candidate, offering refreshments, and escorting them around the office. All these activities require a tremendous amount of time and energy. With one-way video interviews, all you have to do is customize the interview questions and send invitations to all applicants. Candidates will then record their answers at their own convenience and you can review the response whenever you have time.

Give more insight:
A phone interview does not give you enough insight into a candidate’s soft skills. You are talking with the candidate on the phone, you can only hear their voice but can’t see their body language or facial expressions. Video interviewing allows the recruiter to get a glance at the candidate’s personality which is very important to accurately understand when making hiring decisions.

Create a Uniform Interviewing Process:
Employers can ensure that recruiters are utilizing the same interview process with all applicants for all jobs. With video interviewing, all candidates are asked the same questions, given the same amount of response time, and are reviewed by the same team. With Ducknowl, recruiters get a dashboard where they can compare all candidates and their video responses. Video interviewing helps you to develop a standard company-wide interviewing process.

Share Results:
Effectively sharing results of a phone interview is not an easy task. Recruiters have to multitask and take notes during the interview to discuss with hiring managers at a later time. Not only is that time consuming, but oftentimes hiring managers to miss out on important pieces of information about candidates. All of this is avoided with video interviewing. Video interviewing platforms contain tools that allow recruiters to easily share interview responses with hiring managers and other members of their team via email. Hiring managers can quickly view responses from their web browser and include comments and ratings for each candidate.

Eliminate Bias:
Video interviewing tools record all data digitally, you can log in to a dashboard to see all applicants and their resumes with ratings. There is not much room for personal biases, you are asking the same set of questions and rating each of them on the same parameters. With a traditional phone or in-person interview, there are more chances of bias by recruiters since recruiters are just taking notes. When the interview is digital, the bias is minimized.

How to Use Technology to Humanize Recruiting

Applicant tracking systems, online job boards, and social media have all revolutionized the traditional hiring process, improving the efficiency of hiring as well as increasing the pool of candidates by which a prospective employer can pull from. All these technologies have the designed effect of increasing the odds by which high quality talent can be extracted and sourced from the job market. However, concern exists that automizing the recruiting and hiring process will take too much decision making power away from human recruiters, resulting in high quality talent slipping through the cracks because of imperfect algorithms.

This, however, does not need to be the case. A recruiter can now leverage all the benefits of improved sourcing and efficiency, without compromising the personal element of hiring that enables a candidate to differentiate him or herself, as well as allowing a recruiter a more holistic view of a candidate beyond a superficial resume or impersonal phone call. This can be done without the recruiter even having to set aside time out of his/her day for an in-person meeting of a candidate they’re not sure is even the right fit for the role.

Pairing a TSP, or talent screening platform like Ducknowl, with an ATS enables a recruiter to gauge a candidate’s softer skills and knowledge in a manner only previously possible with an in-person interview. Recruiters can now use their human discretion and judgement to determine which candidate stands out among the hiring pool. Paradoxically, technology can now, for the first time, be used to add a human element to recruiting, enabling a recruiter to leverage technology in a manner that reduces its proportional influence over candidate hiring while concurrently increasing the decision making power of the recruiter. We believe this is the equivalent of having your cake and eating it too when it comes to recruiting.

Ducknowl can also function to reduce transparency between recruiter and end-client. The candidate is no longer just a “resource unit,” or a CV/resume, he has a face, a personality, a voice, a story. All too often a candidate might be a perfect fit on paper, but perhaps his personality is a poor fit for the company culture, or perhaps he’s lacking in social acumen in a job where interpersonal ability is paramount. Or conversely, perhaps his experience is lagging but he/she is a goldmine of untapped potential. Algorithms, or code, has no way of determining this. Ducknowl provides the next best thing to having your end-client or hiring manager sitting in on the interview through its “results sharing” feature.

The future of recruiting is harmonizing technology with the human touch. To go forward we must go back. We must yield technology in a manner that gives us more control, not less, lest we lose our humanity in the process.

Why Video Screening Interview is crucial for HR and Recruiters

These days the job market has become very competitive and so has the pool of candidates for a job. Candidates who seem to have good resume doesn’t necessarily mean that they will have very good soft skills like good communication, good presentation or inter-personal skills. Calling candidates on the phone and interviewing them for the soft skills doesn’t necessarily provide the full picture. Based upon my experience, I have come up with 9 reasons on why HR and Recruiters should switch to video interviews.

1. Make it easier to observe the body language

Body language is critical when you are hiring someone. It tells you how confident a person is and how interested the person it in the job. Sometime candidate may not have all the required skills but body language can show you that the person is very interested in the job and have the commitment and dedication. Sometime candidate can have all the requisite but the body language can tell you that person is not very interested or may not have the commitment for the job.

2. Tell you a lot about the personality

In most of the job, personality of a candidate is very crucial factor so that person can be a good team player and grow. You as a recruiter or hiring person, you know that what types of personalities can fit into your environment and the best way to understand that is by video interviews.

3. Prevent the proxy interview

When you conduct phone interviews, how would you know the right person is taking the phone calls and answering your questions. We have learnt that this happens a lot in the technical jobs, where the candidate’s friend who seem to have more experience take the phone interview and crack it. It has happened my personally when I was hiring a Java developer for my company. The video screening will prevent that. Since person’s video will be recorded, so the real person has to submit the video. There can not be any proxy.

4. Make it easier on your schedule

How many times it has happened that you wanted to talk to a candidate at a certain time and the candidate was not available? Or sometime the candidate was available but one of your other team members was not available? Sometime you go back and forth in coming up with the right time. Jobs and candidates move faster in today’s market, if you are not able to interview candidates quickly, you might just loose the candidate. Video interview tool solve this problem. You can schedule the video interview and candidate can give the interview at the convenient time. You can setup an expiration date for the interview, typically most of the recruiters set the expiration time within 24 to 48 hours. Another benefit is that once the candidate has submitted the interview, recruiters and other decision makers for hiring can view the interviews at their availability.

5. Make it easier to compare candidates

That is another benefit that comes with video screening tools. Generally they provide the option to rate candidates based upon the video response submitted. All hiring decision makers can view the video response together and than compare them. This is something not possible when you are conducting in-person interviews. Many times it helps the hiring team to learn more about the type of talent available in the market for a given job and adjust the bar.

6. Reduce your time compared to in-person interview

If you invite 10 people to come to your office for in-person interview it will require lot of time investment from your team. Not only time, it may cost you money as well when you bring people in your office for in-person interview. Conduction video interview helps you overcome these costs and make the decision making faster. Why should you reimbursement candidates to come to your office when you can do that online on a a video screening tool.

7. Save the transportation cost for the candidate

Most of the times, job seekers are not very rich. Inviting them to your office may require them to travel to your city or spend money in lodging. It ads extra burden on candidates to travel. If the person is local then it is not a big issue, but many good candidates may be from out of town. To make it more convenient and less expansive for all the applicants, video interviews is a very good option. Specially in this global economy when we are hiring candidates from different states and sometime from different country.

8. Focus your energy on the right candidate

When you screen multiple candidates via video interviews, you can shortlist 2-3 final candidates and focus your time on them. You can conduct technical skill tests, aptitude test and in-person interviews.

9. Provide more value than a phone interview

Overall, video screening interviews provide more value than the traditional phone interviews. They provide more insight on candidate’s personality, body language, and oral skills. Video screening also reduce the time and money associated with phone interviews or in-person interviews. In todays digital economy, everything is going digital then why not interviews.