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Suppose you’re an iOS developer preparing for a job interview. In that case, these questions are best for you to qualify for your interview: I’ve collected over 100 of the top iOS interview questions and answers for beginners and experienced developers about iOS, Swift, UIKit, SwiftUI, and more. If you’re looking for iOS interview questions for freshers or experienced persons, you are on the right page.

Basic iOS Interview Questions and Answers

1. What is an iOS developer, and what are his duties?

An iOS developer is a programmer or software engineer who develops and designs applications that run Apple’s iOS devices. The iOS developer should be skilled in two programming languages, i.e., Objective-C and Swift.

Responsibilities of an iOS developer:

• Clean, efficient coding for iOS applications.
• Ensure clean and secure codes by executing troubleshooting and bug fixes for applications.  Develop innovative solutions to fulfill the business requirements of clients.
• Supporting all aspects of application development, including design, testing, release, and support.
• Evaluating, implementing, and exploring new technologies continuously to maximize development efficiency.

2. Explain what Swift programming language is.

Swift is a programming language for creating applications for iOS and OS X. Swift has safe programming patterns and additional features that make programming easier and more flexible. Swift is friendly to beginners. It allows programmers to experiment with Swift code and get the results immediately. It is an advanced programming language for Cocoa and Cocoa Touch. Download Xcode and use resources to build applications for all Apple platforms.

3. What do you mean by overlays in OS?

Overlays is a programming method that divides processes into components to save instructions in memory. It does not require any kind of support from OS. It can execute programs that are bigger than physical memory.

4. State the difference between an array and a set.

• Arrays are an ordered collection of values. At the same time, sets are an unordered collection of specific values.
• Each element in a set can only appear one time. At the same time, an array can duplicate elements.

5. What are tuples, and why are they useful in Swift?

In Swift, a tuple is a group of multiple values. Tuples occupy the space between dictionaries and structures. They are commonly used to return different values from a function call.

6. What is the purpose of NotificationCenter?

As you can guess from the name, it deals with notifications. Most people use this to receive system messages, but you can also send your messages inside your application.

7. What are conditional conformances in Swift?

If you are an experienced iOS developer, you should know that protocol conformances permit us to conform a protocol only when certain conditions are fulfilled – hence “conditional conformance.”

8. What is the purpose of the ButtonStyle protocol in Swift?

ButtonStyle Protocol allows us to customize new button styles that can reuse without introducing new views or copy-pasting the styling code to get constant designs.

9. When would you use GeometryReader?

GeometryReader permits us to read the size and location of a view, which means we can create symmetrical layouts or create adaptive modifiers that alter their values as a viewer moves around the screen.

10. What is the purpose of IBDesignable?

Marking a custom view as IBDesignable allows Xcode to preview it when editing storyboards. It’s useful when you create your custom view subclasses and want to see them rendered live in IB, particularly when you want to set their properties there too.

11. What type of settings would you store in your Info. plist file?

The Info. list file stores settings that must be available even when the App isn’t running. You could talk about custom URLs, privacy permission messages, custom fonts, whether the App deactivates background running, and so on.

12. What is the purpose of raw strings in Swift?

Raw Strings (by placing a hash before and after your string quotes) allow us to create strings that will print what you see. As you know, certain escape orders can make our strings print differently.

13. How can an observable object announce modifications to SwiftUI?

Two primary ways are using the @Published property wrapper or calling the object will change. send() directly.

14. What are the advantages of using child view controllers?

A view controller gains access to events like viewDidLoad and viewWillAppear, even when used as a child, which can be useful for many types of UI code. It’s notable how child view controllers can also make our code reusable because the child can be used in other parent view controllers.

15. Are closures value or reference types?

Closures are reference types. If you allocate 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.

16. Can you explain a circular reference in Swift?

A circular reference happens when two objects hold a strong reference to each other and can be a reason for memory leak because neither of the two objects will ever be deallocated. You cannot deallocate the object as long as there’s a strong reference to it, but each keeps the other object alive because of its strong reference.

17. How can you add a stored property to a type by using an extension?

No, it is not possible. You can use an extension while adding a new behavior to an existing type but cannot change the type itself or its inheritance. If you add a stored property, you need extra memory to store the new value. An extension cannot manage such a task.

18. What are the Half Open Range Operators in Swift?

Swift supports different types of operators. One of them is the Half Open Range operator. This operator specifies a range between values a and b (a<b) where b is not included. It is a half-open range operator because it consists of its first value, not only the final value.

19. What is Nested Function in Swift?

A function inside a function is called a nested function.

20. Define Regular Expression?

Regular expressions are the special string patterns that specify how to search for a string.

21. Define Responder Chain?

Responder Chain is the order of objects that get the opportunity to respond to the events.

22. Write names of different types of literal does Swift language have?

Different types of literal are:

• Binary Literals
• Octal Literals
• Hexadecimal Literals
• Decimal Literals

23. What is processor management?

Processor management provides tools and resources for analyzing, defining, optimizing, and controlling business processes for better performance.

24. State the different control transfer statements used in Swift.

Swift language consists of the following Control transfer statements:

• Continue
• Break
• Fallthrough
• Return

25. What do you mean by Optional Chaining in Swift?

In Swift programming language, Optional Chaining is a process of querying and calling properties. You can chain different queries together, but if any link in the chain is nil, the whole chain fails.

26. How do you explain inheritance in Swift?

Inheritance is a process in which a class can inherit properties, methods, and other features from another class. It is supported in Swift Programming language. There are two types of classes in inheritance in Swift:

• Subclass
• Super Class

27. What is Process management in iOS?

Each process in iOS is made up of one or more threads. Each thread acts as a single path of execution. Each application in iOS starts with a single thread, which runs the application’s main functions.

28. Write names of components of Process Control Block?

Following are the components of Process Control Block:

29. State different Process States in OS.

Processes in the operating system can be in any of the following states:

• New: the process is being created.
• Ready: The process is waiting to be assigned to a processor.
• Running: Commands are being executed.
• Waiting: Process is waiting for some event to occur.
• Terminated: The process has completed execution.

30. How can you write a comment in Swift?

You can write a single-line comment with double slashes(//).

Example:

// This is a single-line comment.

Multi-line comments:

Multi-line comments are written with a forward-slash followed by an asterisk (/*) and end with an asterisk sign by a forward slash (*/)

For Example:

/* This is multiLine comment*/

31. How is Switch Statement used in Swift language?

The switch statement is used as a substitute for the long if-else-if statements.

Switch Statement supports any data, synchronizes the data, and checks for equality.

The switch statement must have covered all possible values for your variable.

32. What is the use of break statement in Swift language?

The break statement is used in a loop where you have to end a statement immediately. It is also used to end a case in a switch statement.

iOS Interview Questions For Experienced

33. Define Core Data?

Core Data is an object graph management framework that controls a potentially very large graph of object instances. It allows an app to work with a graph that would not fit into memory by faulting instances in and out of memory as required. Core Data also contains constraints on properties and relationships and maintains reference integrity (e.g., keeping forward and backward links consistent when objects are added/removed to/from a relationship). Core Data is thus an ideal framework for developing the “model” component of an MVC architecture.

To implement its graph management, Core Data uses SQLite as a disk store. It could have been implemented using a relational database or even a non-relational database such as CouchDB. Core Data is not a  database engine as an API abstracts over the actual data store. Core Data can save as an SQLite database, a list, a binary file, or even a custom data store type.

34. Explain what NSUserDefaults is? NSUserDefaults support Which types?

NSUserDefaults is the easiest way to store data without a database using key-value pair. NSUserDefaults stores a small amount of data. In most cases, NSUserDefaults is best used to save users’ settings and data that is not critical. Following are types supported by NSUserDefaults:

• NSString
• NSNumber
• NSDate
• NSDictionary
• NSData

Pros

• Relatively easy to store and retrieve data
• Perfect for keeping small size data (example: User’s Settings)
• Easy to learn and implement

Cons

• Not suitable to collect a large amount of data
• The performance will slow down when storing a large amount of data
• Not ideal for storing sensitive data

35. For what purpose reuseIdentifier used?

It is a basic iOS interview question and is most commonly asked in interviews. The reuseIdentifier is used to collect together parallel rows in an UITableView. A UITableView will normally assign just enough UITableViewCell objects to display the content visible in the table.

36. State the difference between viewDidLoad and viewDidAppear?

viewDidLoad only appears on the screen when the view is loaded, whether from a Xib file, storyboard, or programmatically created in loadView. viewDidAppear appears every time on the device. If data is static and does not seem to be changed, it can be loaded in vieDidLoad and cached. However, if the data changes regularly, vieDidAppear can load it. The data should be loaded non synchronously on a background thread to avoid blocking the UI in both situations.

37. What do you prefer when writing UI’s? Xib files, Storyboards, or programmatic UIView?

When going for an iOS interview, you must know the strategy of writing UI’s. Storyboards and Xib’s are great to produce quick UI’s that match a design spec. It is also easy for product managers to see how far along a screen is visual. Storyboards are also good at representing a flow through an application and giving a high-level visualization of a whole application. Storyboard’s drawbacks are that they are difficult to work on collaboratively in a team environment because they’re a single file and merging becomes difficult to control. Storyboards and Xib files can also suffer from duplication and become complex to update. For example, if all buttons need to look alike and suddenly need a color change, it can be a long/difficult process across storyboards and Xibs. Programmatically constructing UIView’s can be effusive and boring, but it can allow greater control and easy separation. It also shares code. And you can also test them very easily.

Most developers will prefer a combination of all three to allow sharing code, then reusable UIViews or Xib files.

38. What are different methods to identify the layout of elements in UIView?

Following are a few common ways to specify the layout of elements in UIView:

• Using InterfaceBuilder, You can add a XIB file to your project, including layout elements, and then load the XIB file in your application code. You can build a storyboard for your application using InterfaceBuilder.
• You can write your code to use NSLayoutConstraints to have elements in a view arranged by Auto Layout.
• Create CGRect to describe the exact coordinates for each element and pass them to UIView’s.

39. What is the significance of “?” in swift language?

The question mark makes a property optional if declared. If the PropertyProperty does not hold value, the “?” helps avoid runtime errors.

40. What are synchronous and asynchronous tasks in iOS?

If you are an experienced iOS developer, you must know synchronous and asynchronous tasks in iOS. When you perform the synchronous tasks, you have to wait for the task to complete before proceeding. On the other hand, when you perform tasks asynchronously, you don’t have to wait to complete tasks. You can perform the tasks simultaneously. When tasks are completed in the background, will notify you.

The figure clearly explains that synchronous tasks take more time to complete while asynchronous tasks run simultaneously and take less time to complete.

41. Explain de-initializer and how it is written in Swift?

Before the de-allocation of a class instance, a de-initializer is declared immediately. You write de-initializer with the deinit keyword. It is written without any parenthesis as it does not take any parameters. It is written as

Deinit    {

// perform the deinitialization

}

42. What do you mean by lazy stored properties, and why is it useful?

Lazy stored properties are used for a property whose first values are not calculated until the first time it is used. You can claim a lazy stored property by reporting the lazy modifier before its declaration. Lazy properties are beneficial when the initial value relies on outside factors whose values are unknown.

43. What is the purpose of Size Classes?

Size classes allow you to add extra layout configuration to your App so that your UI works well across multiple devices. For example, you can say that a stack view lines up its views in normal conditions horizontally but vertically when constrained.

44. Which JSON framework is supported by iOS?

iOS supports the SBJson framework. SBJson is a JSON syntax analyzer (parser) and generator for Objective-C. It is making JSON handling easier by providing flexible APIs and additional control.

45. Explain the difference between atomic and nonatomic properties?

Atomic properties are thread-safe (something is shared across different threads without issues like a crash), but it is slow. Nonatomic properties mean different threads access the variable (dynamic type). Non-atomic means thread-unsafe, but it is fast.

46. What are the different kinds of iOS Application States?

The different application states of iOS are:

• Not running state
• Inactive state
• Active state
• Background state
• Suspended state

Not running state: When the App has not been launched or was running but was ended by the system.

Inactive state: The App is running in the foreground but currently not receiving any events. It remains inactive only when the user locks the screen or prompts the user to respond to an event such as an SMS message or a phone call.

Active State: When the App is running in the foreground. It is also receiving events.

Background state: When the App is in the background state, it executes code. Most applications enter this state briefly to being suspended. However, an app that requests extra execution time can stay in this state for some time. Also, an app directly launched into the background enters this state instead of the inactive state.

Suspended state:  A suspended app remains in memory and does not execute any code.

47. How many ways to achieve concurrency in are iOS are?

To achieve concurrency in iOS, there are three different ways.

• Threads
• Dispatch Queues
• Operation Queues

48. What is SpriteKit, and what is SceneKit?

SpriteKit is a framework for the easy development of animated 2D objects.

SceneKit is a framework from OS X that helps with 3D graphics design.

SpriteKit, SceneKit, and Metal frameworks are expected to run a new generation of mobile games that redefine what iOS devices’ powerful graphics processing units can offer.

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49. Explain the difference between ‘assign’ and ‘retain’ keywords?

‘Assign’ keywords specify that the setter(sets or updates values) uses simple assignment. It is used in attributes of scalar type like float, int.

‘Retain’ keywords specify that you should call retain on the object upon assignment. It takes ownership of an object.

50. Define layer objects?

Layer objects are data objects that manage visual content and use views to display their content. Custom layer objects provide options for modifying complex animations and other types of the visual appearance of that content.

51. What is an autorelease pool in Swift?

An autorelease pool stores objects that send releases to all objects when the pool itself is drained. If you utilize Automatic Reference Counting (ARC), you cannot utilize the autorelease pool directly. You utilize @autoreleasepool blocks.

52. Kindly explain the class hierarchy for a UIButton until NSObject?

UIButton inherits from UIControl, UIControl inherits from UIView, UIView inherits from UIResponder, UIResponder inherits from the root class NSObject.

53. Which API would you use to write test scripts to use the application’s UI elements?

UI Automation API is utilized to automate the test procedures. JavaScript test script simulates user interaction with the application and returns log information to the host computer.

54. Which is the application thread from where you should use UIKit classes?

You can use UIKit classes from an application’s main thread.

55. Differentiate ‘app ID’ from ‘bundle ID’. Why are they used?

An App ID is used to identify one or more applications from a single development team. It consists of a Team ID and a bundle ID search string separating the two parts with a period (.). The Team ID is supplied by Apple and is particular to a specific development team, while the developer supplies the bundle ID search string. Whereas the bundle ID is defined by each App and is specified in Xcode. A single Xcode project has different targets and therefore outputs multiple apps.

56. State the difference between Cocoa and Cocoa Touch?

The two most commonly used application frameworks for building applications are Cocoa and Cocoa Touch. However, they vary in the following ways: 

57. Which programming languages are used for iOS development?

Following are programming languages used for iOS development:

• HTML5
• .net
• C
• C++
• Swift
• JavaScript
• Objective-C

58. What is Automatic Reference Counting (ARC)?

In Swift programming language, automatic reference counting is used to manage apps’ memory usage. It initializes and deinitializes system resources. ARC keeps track of how many properties, constants, and variables refer to each class instance. When there is at least one active reference to any instance, ARC will not deallocate them. Its use is an essential part of iOS development.

Functions of ARC:

• ARC creates a new class instance using init() and allocates a piece of memory to store the information.
• Memory caches information about the instance type and its values.
• As soon as the class instance is no longer needed, ARC automatically frees memory by calling deinit().
• By tracking current referring classes’ properties, constants, and variables, ARC makes sure that deinit() is only involved in instances not used.

59. Explain what is Grand Central Dispatch (GCD) in iOS?

Grand Central Dispatch (GCD) is a low-level API that allows users to run concurrent tasks(run simultaneously). It also manages threads in the background. Apple’s solution is to build concurrency and parallelism into iOS applications so different tasks can run concurrently in the background without affecting the main thread. GCD was introduced in iOS 4 to avoid the tedious serial execution of tasks.

60. What do you mean by Deep linking in iOS?

Deep links are those links that send users directly to an app instead of a website or store using uniform resource locator (URL) or universal links. The URL scheme is a well-known method of having deep links, but Universal Links are Apple’s new approach to connect your web page and your App under the same link. Deep linking involves creating a clickable link that opens up your App and a smart one that navigates to the resource you require. Users are headed straight to in-app locations using these links, which saves them the time and effort of seeing those pages themselves, thus enhancing their user experience tremendously. 

Explanation: If you use the URL https://www.temok.com/, you may open the Temok website. However, if you use https://www.temok.com/linux-shared-hosting-usa, you will open Linux-shared hosting plans for the USA on the Temok website.

61. Which framework is used to build an application’s interface for iOS?

The foundation framework defines classes, protocols, and functions for iOS and OS X development; UIKit is specifically designed for iOS development. The application’s user interface and graphical infrastructure are developed using UIKit in iOS. It includes:

• App Structure( manages the interaction between system and user)
• Event Handling (handles different gestures like input gestures, multi-touch gestures, etc.)
• User Interface (provides user interactions, sharing text and content, choosing images, editing videos, print files, etc.)
• Graphics, Drawing, and Printing

62. Explain Objective-C in OS.

Apple has used Objective-C as an object-oriented programming language since the 1990s. This language compromises the benefits of two earlier languages – C and Smalltalk.

Features:

• In Objective-C, metaclasses are automatically created and managed during runtime.
• Both typing is supported; dynamic typing and static typing.
• It is easy to understand.

63. Name the most important data types in Objective C?

The following are the important data types that most developers use in Objective C.

BOOL: It represents a Boolean value that is neither true nor false. Both the _Bool or BOOL keywords are valid.

Example:

_Bool flag = 0;

BOOL second flag =1;

NSInteger: Represents an integer

Example

Typedef long NSInteger;

Typedef int NSInteger;

NSUInteger: Represents an unsigned integer.

Example:

typedef unsigned long NSUInteger;

typedef unsigned int NSUInteger;

NSString: Represents a string

Example:

NSString *greeting = @”Hello”;

64. What are the important features of Swift?

Swift programming language is being developed to write correct codes and maintain them easily. It offers the following features:

Safety: Swift is an efficient way to write code. Checking code before execution is very important. It removes an unsafe code before it is used in production.

Simple Syntax: Its syntax is easy to use, learn and understand. Its features make able you to write more expressive code.

Readability: Swift has a simple syntax, easier to read and write. It is easier for developers to write swift code since it is more like plain English, allowing them to spend less time.

Multiplatform Support: Swift is fully supported with iOS, macOS, tvOS, watchOS, Linux, and many other platforms. It means you can develop software that is compatible with all operating systems.

Open-Source: Swift is an open-source framework developed at swift.org. Swift supports all Apple platforms and makes programming easier, safer and faster.

Compatible with Objective C: Swift programming language has full compatibility with Objective-C. It allows developers to import frameworks from Objective-C using Swift syntax. Developers can use Objective-C libraries and classes inside swift code.

65. Explain Dictionary in Swift.

Swift programming describes a dictionary as an unordered collection of items. It stores items in key-value pairs. A dictionary uses a specific identifier called a key to store an associated value which can be referenced and recovered through the same key.

Syntax:

 var Dict_name = [KeyType: ValueType] ()

Example:

var examresult= [“Nick”: “34”, “Aditya”: “26”,  “Emma” : “94”]

print(examresult)

Output:

[“Nick” : “34”, “Aditya” : “26”, “Emma” : “94”]

In the above example, we have a dictionary named examresult. Here,

Keys are “Nick,” “Aditya,” “Emma”

Values are “34”, “26”, “94”

66. Why are design patterns important? Name some of the famous design patterns used in iOS?

A design pattern is a solution to a specific problem you might experience while designing an app’s architecture. These patterns are templates designed to make coding easier and allow them to reuse. Following are some of the design patterns that you can use in iOS.

• Model-View-Controller (MVC)
• Model-View-View-Model(MVVM)
• Façade Design Pattern

Model-View-Controller: It is designed for developing web applications in which these components are connected, i.e., view, controller, and model. The user interface conceives views shown to the end-user at a certain point in time. The model manages the data of your application. The collector acts as a link between view and model. There is always a connection between these three components.

Model-View-View-Model (MVVM): Unlike MVC, there is a special layer in MVVM called the view Model between the view and the model. Using the view model design pattern, you can transform model information into values shown on the view. There is also a binding link between the view and View model that allows the view model to share updates with the view.

Façade Design Pattern: this design pattern provides a simplified interface to a complex set of classes, frameworks, or libraries. Developers often use this design pattern when a system is complex to understand. This pattern hides the difficulties or complexities of the larger system and provides a simpler interface to the client.

67. Explain the difference between KVC and KVO in Swift.

KVC (Key-value-coding)

It allows object properties to be accessed at runtime using strings rather than knowing the property names statically during development.

KVO (Key-Value Observing)

KVO is one of the methods for observing program state changes in Objective- C and Swift. If an object has instance variables, KVO makes other objects observe the modifications or changes to those variables.

68. Explain iBeacons in iOS.

iBeacon, Apple’s new low-energy Bluetooth wireless technology, permits iPhone and other iOS users to receive location-based information and services on smartphones. iBeacons are small, wireless transmitters that convert signals to nearby smart devices via Bluetooth low energy technology.

69. Define the function of the completion handler.

Completion handlers are just functions passed as parameters to other functions. They are used to dealing with asynchronous tasks since we do not know when they will end. Completion handlers tell an application when an operation, such as an API call, has been completed. The program is notified that the next step needs to be completed.

70. State the difference between strong, weak, read-only, and copy.

Strong: This PropertyProperty maintains a reference to PropertyProperty throughout the lifetime of an object. When you declare strong, you expect to “own” the object you are referencing. Data you assign to this PropertyProperty will not be destroyed as long as you or any other object references it strongly.

Weak: It means that you should keep the object in memory as long as someone points to it strongly, and you don’t require control over its lifetime.

Read-only: Initially, an object’s PropertyProperty can be defined, but it cannot change or alter.

Copy: This attribute is an alternative to a strong attribute. To take ownership of a current object, it creates a copy of whatever you assign to the PropertyProperty, then takes ownership of that copy.

71. Explain Test-Driven Development (TDD).

Test-Driven development is used in the development of software. In TDD, developers plan the software characteristics that they want to create and then write test cases for each characteristic before implementing it. Through test-driven development, we can get insight into both the quality of the implementation (does it work) and the design quality (is it well structured).

In the first case, the test case will fail because the code is not yet implemented, and this is usually referred to as the red phase. After that, code is written to ensure that the test case passes and does not break any components or current test cases; that phase is called the green phase. The developer should then refactor the implementation of the code by maintaining and cleaning the codebase and optimizing the efficiency. Repeat this process every time a new test case is added.

72. How can you execute storage and persistence in iOS?

Persistence means storing data on the disk to be retrieved without being modified the next time the App is opened. From simple to complex, there are the following methods for storing data:

• Data structures such as arrays, dictionaries, sets, and other data structures are real or perfect for storing data intermediately.
• NSUserDefaults and Keychains are both simple key-value stores. NSUserDefaults is unsafe, whereas Keychains is safe.
• A file or disk storage is a way to store data to or from a disk using NSFileManager.
• Relational databases, such as SQLite, are good for implementing complex querying structures.

73. How do you explain generics in Swift and write its usage?

An important feature of Swift is generics, and much of the Swift standard library is written in generic code. Swift’s ‘Array’ and ‘Dictionary’ types, for example, constitute generic collections. Generic code lets you create flexible, reusable functions and types that operate with any data type. You can create code that does not get too specific about underlying data types, resulting in cleaner code. Generics are used to avoid repetition and to provide extraction.

Example:

Func swapping (x: inout Int, y: inout Int)

{

  let temp = x

  x = y

  y = temp

}

var num1 = 20

var num2 = 20

print (“Before Swapping: /(num1) and /(num2)”)

Swapping(x: &num1, y: &num2)

Print(“After Swapping: /(num1) and /(num2)”)

Output:

Before Swapping: 20 and 60

After Swapping: 60 and 20

In the above example, we have defined a function called swapping() to swap integers. There are two parameters, x, and y, of int type. As seen in the output, x and y are exchanged after the swapping.

74. What is Enumerations or Enum in Swift?

The term enumerations refers to a user-defined data type consisting of a set of related values that enable you to work with those values in your code in a type-safe manner. The keyword enum defines this data type.

75. Write the two different smart groups in Xcode?

Smart Groups are divided into two parts:

• Simple Expression Smart Group
• Simple filter smart group

76. Explain what TVMLKit is.

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

77. What is Code Coverage?

Code Coverage is used to estimate the value of our unit tests. Its measurement specifies which statements in a body of code have been executed and which statements have not been executed through a test run. Unit tests assist in making certain functionality and provide a mechanism of verification for refactoring efforts.

78. Define Operator Overloading?

Operator overloading can work on how existing operators perform with existing types. To overload an operator, we use a unique operator function. Operators are those symbols like +, /, and *.

79. Describe the role of design patterns in Linux?

Design patterns are used in solving common problems in software design. It helps you write code that is easy to understand using different templates. Following are some common Cocoa Design patterns:

Creational: Singleton

Behavioral: Observer and Memento

Structural: Decorator, Adapter, Façade

80. What is Adapter Pattern?

An Adapter admits classes with adverse interfaces to work in a sink attach itself around an object and disclose a standard interface to link with that object.

81. Explain the observer Pattern?

The observer pattern is used to alert other objects of any state changes. Observer lies in the category of behavioral pattern. It specifies the communication between objects: observable and observers. For example, a news agency notifies all channels when it receives any news.

82. Mention the Realm benefits?

• A realm is a security policy domain defined for an application server or a web.
• Realm is an open-source database framework.
• It is implemented from scratch.
• It is faster and faster than core data.
• All documents related to Realm are written properly, and experts can find an answer on the official website if required.

83. Write down the names for battery-efficient location tracking?

It is one of the most commonly asked iOS interview questions.

Following are the three types of APIs:

• Significant location changes
• Region monitoring
• Visit events

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

Region Monitoring: It tracks all enter/exits possibilities from circular regions with a radius equal to 100m or more. It is the most accurate API after GPS (Global Positioning System)

Visit Events: Monitoring place Visit Events entering/exiting from a place (home/office).

84. What is the most efficient way to cache data in memory?

There are many ways of making caches with a simple dictionary, but whatever you select, you should be prepared to explain your choice why you like it. Ensure and consider how you remove data from the cache, either explicitly or to hit a memory quota.

If you feel comfortable talking about it, NSCache is preferable over a simple dictionary because it automatically clears the cache when memory is low.

85. Explain the architecture of iOS.

iOS works in a Layered structure. iOS Architecture comprises four layers, each of which presents a programming framework for developing applications that operate on top of the hardware. The layers between the Application Layer and the Hardware Layer will enhance communication. A lower-level layer provides the services that all applications need, while an upper-level layer (or high-level layer) provides graphics and interface-related services.

Core OS ( or Application) Layer: Core OS Layer models directly on top of the device hardware and is the bottom layer of the iPhone OS stack. In addition to basic operating system services, such as memory management, handling of file systems, and threads, this layer delivers low-level networking, access to external accessories, etc.

Service Layer: It aims to design the services that upper layers or users require. Its other essential features are blocked objects, Grand Central Dispatch, in-app purchases, and iCloud storage. ARC Automatic Reference Counting has supported the service layer.

Media Layer: It manages media like video, audio, graphics, etc. The media layer will permit us to use all graphics, video, and audio technology of the system.

Cocoa Touch Layer: It is also called the application layer. It is the place where frameworks are made when applications are built. In addition, it works as the interface for iOS users to operate with the operating system. It contains touch and motion capabilities.

86. What do you mean by Property in iOS?

Properties are those values associated with a class, structure, or enum. They can be considered “sub-variables,” i.e., parts of another project.

87. For what purpose are computed properties used?

Computed Properties are used to calculate the values instead of storing them. These are usually provided by the classes, structures, and enumerations.

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88. State the difference between Android and iOS.

Android:

• It is the mobile operating system for Android devices offered by Google LLC.
• It is specially developed for smartphones and tablets.
• It is mostly written in C, C++, Java, and other languages.
• Google Chrome is the default browser on Android devices. However, you can install aby another browser.
• The Android software is available for many manufacturers comprising Samsung, LG, etc., which could be the reason for some quality issues in cheaper phones.
• Contrary to this, the performance of Android devices may decline over time.
• Android devices have open-source code; you can modify your phones and tablets operating system at their discretion.

iOS:

• It is the operating system for Apple devices presented by Apple incorporation.
• It is specially developed for Apple iPhones, iPods, and iPads.
• It is mostly written in C, C++, Objective-C, Swift, and other languages.
• Safari is the default browser on iOS devices. However, you can install many other browsers.
• Apple has strict quality over iOS, and there are no quality problems.
• iOS devices run at consistent speed over time.
• iOS is a closed system. The source code of Apple’s apps isn’t accessible for developers; iPhone and iPad owners can’t change the code on their devices. It makes iOS devices harder to hack.

89. Explain NSError in Swift.

Information about an error condition is summarized within an NSError object flexibly and object-oriented manner. An NSError consists of three basic attributes: a predefined error domain, a domain-specific error code, and a user info dictionary comprising application-specific information.

90. What do you mean by dynamic dispatch?

In simple words, dynamic dispatch means that the program decides at runtime which implementation of a specific method or function it requires to call on. When a subclass overrides a method of its subclasses, dynamic dispatch defines whether to call the subclass implementation of the method or the parents.

91. What is a Pipe, and when is it utilized?

A pipe is a connection between two or more processors that are interrelated to each other. It is a mechanism used for inter-process communication using message passing. One can easily send information such as the result or output of one program process to another using a pipe. It can be used when both processes want to communicate one-way, i.e., inter-process communication (IPC).

92. State the difference between Structure And Class?

In Swift Programming language, structure is value types and class is reference types. When you copy a structure, you finish up with two specific copies of the data. When you copy a class, you finish up with two references to one object of the data.

93. What are the different kinds of operations that are possible on semaphore?

Two atomic operations are possible:

• Wait()
• SIGNAL()

94. What do you mean by RTOS?

Real-Time Operating System (RTOS) is an operating system used for real-time applications, i.e., for those applications where data processing should be done in a fixed and small amount of time. It performs very well on tasks that must execute within a short time. It also manages execution tasks, monitoring, and all-controlling process. It also occupies less memory and consumes few resources.

95. What do you mean by process synchronization?

Process synchronization is a way to interrelate processes that use shared resources or data. It is very much important to make sure synchronized execution of cooperating processes. It will maintain data consistency. It shares resources without any interference using mutual exclusion. There are two types of process synchronization:

• Independent Process
• Cooperative Process

96. Write different names of IPC mechanisms?

Pipes

• Messaging Queuing
• Semaphores
• Socket
• Shared Memory
• Signals

97. What is the difference between Stack And Heap?

Stack is easy to use as compared to Heap. Heap is quite slow.
Stack’s kept in RAM on the computer while Heap creates memory problems.
Stack is quite fast while Heap is created at runtime.

FAQs Related To iOS Development Career

98. Is an iOS developer a good career in 2023?

An iOS developer is an in-demand career that offers good salaries and job security. iOS developers perform challenging projects and contribute to different projects. There are huge job opportunities in the iOS field that provide good packages and better career growth in development. iOS application development is one of the lucky jobs you can do remotely.

99. What are the job roles of iOS developers?

Some of the job roles in the field of iOS development are below:

• Engineer
• Software Engineer
• Software Developer
• Architect
• iOS developer
• Senior iOS Developer
• Lead Developer
• Principal Developer
• Principal Engineer
• Associate Software Engineer

100. What skills are required to become an iOS developer?

You have to learn these languages to become an iOS developer. Following are the top skills you required for an iOS Developer:

• Swift Programming Language
• iOS Platform
• C-based Libraries
• APIs and Cloud Messaging
• Design Guidelines
• Spatial Reasoning
• UI and UX Designing
• Core Data
• Grand Central Dispatch (GCD)
• Networking

101. What are the major roles and duties of an iOS developer?

An iOS developer designs and creates advanced applications for the iOS platform. iOS developer makes sure the quality of the application. Collaborate with cross-functional teams to develop and send new features. An iOS developer tests code for robustness and reliability. Improves application performance and fixes application bugs. Implement all application updates. An iOS developer always discovers, evaluates, and implements new technologies for maximum efficiency.

102. What are the academic requirements to become an iOS developer?

To become an iOS developer, you’ll need to have a Bachelor’s degree in Software Engineering, Computer Science, IT, or any other related field. Also, some senior positions may require experience a few years off in software development experience or iOS development.

103. How much time is required to learn iOS development?

If you are a beginner or a fresher, it would require at least six months to learn iOS development from scratch. If you can study for several hours per day, you can learn much faster. In a few months, you’ll become an iOS developer know all the basics of iOS, and be able to develop a simple iOS application. In this article, all basic iOS interview questions are that you can easily crack an interview for an internship or highly paid job.

Conclusion

Many Apple devices are in use worldwide. IOS users worldwide have been rising rapidly, which is a good sign for iOS app developers. In this article, we have put together the top 100+ of the most commonly asked iOS interview questions to help you succeed at your iOS job interview. iOS developers also need to stay updated on changes in the iOS community. Ensure you read Apple developer news, listen to podcasts and read blogs.

Hopefully, these answers will be useful in better understanding iOS basics, Swift, and advanced topics. Anyone looking to flourish in an iOS interview would benefit from knowing the answers to these Swift and iOS developer interview questions. Good luck with your interview!