Are you preparing to break into a career as an iOS developer? If yes, ease the stress and brush up on some of the skills you haven’t used in a while – you are all set to go. The demand for iOS developers is expected to shoot through the roof due to the adoption of iOS devices.

Let’s take a look at some of the top IOS interview questions and answers, which will be a great self-test if you are seeking some practice for your IOS interview.

Top IOS Interview Questions and Answers

Q1. What is ARC?

Ans. ARC (Automatic Reference Counting) is a compiler level feature that defines the process of managing the lifetime of objects in objective-C.

Q2. Define Bundle ID?

Ans. The bundle ID is used for both OS X apps and iOS.  It uniquely defines every iOS application. A bundle identifier can recognize any update to your app.

Q3. Name some important data types found in objective-C?

Ans. There are four data types which are as follows:

  • Bool
  • CGfloat
  • NSintegar
  • NSstring

Q4. Define Cocoa/Cocoa touch?

Ans. It is used for building software codes to run on iOS for the iPad and iPhone. Cocoa Touch is written in the objective-C language and has a different set of graphical control elements to Cocoa.

Q5. What are the programming languages used for iOS development?

Ans. Programming languages used for iOS development are:

  • HTML5
  • .NET
  • C
  • Swift
  • Javascript
  • Objective-C

Q6. What are the methods to achieve concurrency?

Ans. The methods to achieve concurrency are:

  • Dispatch queues
  • Threads
  • Operation Queues

Q7. What is the difference between atomic and nonatomic synthesized properties?

Ans. Atomic:

  • Default behavior
  • Not fast
  • Make certain the process is completed entirely by CPU

Nonatomic:

  • Not default behavior
  • Faster
  • Not able to deal with multiple requests at the same time

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Q8. When is an app said to be in not running the state?

Ans. It is said when it is not launched or gets terminated by the system while running.

Q9. Explain the object?

Ans. Objects are mainly the variables that are of class types. It can be a function, method, data structure, or a variable.

Q10. When would you say that an app is in an active state?

Ans. An app is said to be in an active state when it is accepting events and running in the foreground.

Q11. Which framework is used to construct the application’s user interface?

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

Q12. What is iBeacon?

Ans. iBeacon enables mobile apps to listen to signals from beacons in the physical world and respond accordingly. It comprises of two parts: a broadcaster and a receiver.

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Q13. What is Method Swizzling?

Ans. The process of changing the implementation of an existing domain, Method Swizzling, enables you to write that code that can be executed before or after the original method.

Q14. When is the category used?

Ans. It is used to add a set of related methods and to add additional methods in the Cocoa framework.

Q15. What is the difference between Viewdidload and Viewdidappear?

Ans. Viewdidload:

  • It is called when it is loaded into memory.
  • Data can be loaded in Viewdidload if it is fairly static and likely to change.

Viewdidappear:

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

Q16. What does KVO stand for?

Ans. KVO means key-value observing, which enables a controller to observe changes to property value.

Q17. Which is the latest IOS development platform?

Ans. The latest iOS development platform is iOS 9.2 beta 2 Build version: 13C5060d

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Q18. What are the two different smart groups in Xcode?

Ans. Smart Groups are divided into two parts:

  • Simple expression smart group
  • Simple filter smart group

Q19. How can you open the Code Snippet Library in Xcode?

Ans. CMD+OTP+Cntrl+2

Q20. Explain what TVMLKit is.

Ans. There is a link between JavaScript, TVML, and tvOS apps, which combines and is known as TVMLKit.

Q21. What is GCD?

Ans. GCD (Grand Central Dispatch) defines as a library that offers object-based and low-level API to execute tasks accordingly when managing threads.

Q22. Mention the features of iOS 12.

Ans. Following are the features of iOS 12:

  • Natural Language
  • Health Records
  • Siri Shortcuts
  • CarPlay
  • ARKit 2

Q23. What are the methods we can follow to achieve concurrency in iOS?

Ans. There are three methods we can follow to achieve concurrency in iOS:

  • Operation queues
  • Threads
  • Dispatch queues

Q24. Which method can we use to perform final utilization before displaying the app to the user?

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

Q25. Explain what Code Coverage is?

Ans. Code coverage is used to calculate the value of our unit tests.

Q26. Explain what the Responder Chain is? 

Ans. A Responder Chain is explained as the hierarchy of objects that have the opportunity to respond to events received.

Q27. What is Operator Overloading? 

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

Q28. Why is the use of a design pattern in Linux? 

Ans. Design patterns are used to solve common problems in software design. These design patterns use different templates to help you write code that is easy to understand. Look at some common Cocoa design patterns:

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

Q29. Explain the Adapter Pattern? 

Ans. An Adapter acknowledges classes with adverse interfaces to work in a sink and tie itself around an object and exposes a standard interface to interact with that object.

These are the most commonly asked IOS Interview Questions

Q30. Explain the Observer Pattern? 

Ans. The Observer pattern is used to notify other objects of any state changes. Cocoa uses the observer pattern in two ways: 

  • Notifications
  • Key-Value Observing (KVO)

Q31. Mention the Realm benefits?

Ans. Following are the Realm benefits:

  • An open-source database framework.
  • Zero copy object-store.
  • Implemented from scratch.
  • Fast.

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

Ans. Following are three types of APIs:

  • 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 are enters/exits from a place (home/office).

These top IOS interview questions and answers will improve your knowledge in IOS and help you crack any IOS job interview.

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