100+ IOS Developer Interview Questions and Answers

The code prints 'Hello World' to the console.

• The code uses the print function to output 'Hello World'.

• There are no variables or conditions involved in the output.

Swift is a programming language developed by Apple for iOS, macOS, watchOS, and tvOS development.

• Swift is a modern, fast, and safe programming language.

• It is designed to work seamlessly with Apple's Cocoa and Cocoa Touch frameworks.

• Swift is used to develop applications for iOS, macOS, watchOS, and tvOS.

• It is open-source and has a large community of developers contributing to its growth.

• Swift is known for its concise syntax and powerful features like optionals, closures, and g...read more

Higher order functions in Swift are functions that can take other functions as parameters or return functions as results.

• Examples of higher order functions in Swift include map, filter, and reduce.

• Higher order functions help in writing cleaner and more concise code by abstracting away common patterns.

• They promote functional programming principles by treating functions as first-class citizens.

Retain, copy, and strong are all memory management keywords in Objective-C used to manage object ownership.

• Retain: Increases the retain count of an object, ensuring it is not deallocated as long as there are references to it.

• Copy: Creates a new copy of an object, ensuring that changes to the original object do not affect the copied object.

• Strong: Similar to retain, it increases the retain count of an object and ensures it is not deallocated as long as there are references to ...read more

A protocol is a set of rules or guidelines that define how objects interact with each other in a specific context.

• Protocols define methods that a class must implement to conform to the protocol

• They can also define properties, initializers, and associated types

• Classes, structs, and enums can adopt protocols to inherit their behavior

Reduce application size by optimizing images, removing unused code, using ProGuard, and splitting APKs.

• Optimize images by using tools like ImageOptim or TinyPNG.

• Remove unused code and resources to reduce unnecessary bloat.

• Use ProGuard to shrink, optimize, and obfuscate code.

• Split APKs to only include necessary resources for each device configuration.

Weak & Unowned references are used in ARC to prevent retain cycles in Swift programming.

• Weak references do not increase the retain count of an object, and automatically become nil when the object is deallocated.

• Unowned references do not keep a strong reference to the object, and can become a dangling pointer if the object is deallocated.

• ARC (Automatic Reference Counting) is a memory management system used in Swift to automatically manage memory for objects.

ARC stands for Automatic Reference Counting, a memory management system used in iOS development. Retain count is the number of references to an object.

• ARC is a memory management system in iOS that automatically tracks and manages memory usage.

• Retain count is the number of strong references to an object, which determines when the object should be deallocated.

• When an object's retain count reaches 0, it is deallocated from memory to free up resources.

• ARC helps prevent memory lea...read more

Class and struct are both used to define custom data types in Swift.

• Class is a reference type, while struct is a value type.

• Classes support inheritance, while structs do not.

• Classes have deinitializers, while structs do not.

• Structs have memberwise initializers, while classes do not.

• Examples of classes: UIViewController, NSObject.

• Examples of structs: CGPoint, CGRect.

The design pattern used for an app and its architecture is crucial for scalability and maintainability.

• Use MVC (Model-View-Controller) for separating data, presentation, and user interaction.

• Consider MVVM (Model-View-ViewModel) for better separation of concerns and testability.

• Implement Dependency Injection to make components loosely coupled and easier to test.

• Use Singleton pattern for managing shared resources like network calls or database connections.

• Consider using Clean A...read more

Solid principles are a set of five design principles for writing maintainable and scalable code.

• Single Responsibility Principle: A class should have only one reason to change.

• Open/Closed Principle: Classes should be open for extension but closed for modification.

• Liskov Substitution Principle: Objects of a superclass should be replaceable with objects of its subclasses without affecting the program's correctness.

• Interface Segregation Principle: Clients should not be forced to ...read more

Structs are value types, classes are reference types. Singletons ensure only one instance of a class. MVC separates concerns, MVVM adds a ViewModel layer.

• Structs are lightweight and copied by value, while classes are more powerful and passed by reference.

• Singletons are useful for global state and ensuring only one instance of a class exists.

• MVC separates concerns by dividing code into Model, View, and Controller components.

• MVVM adds a ViewModel layer between the View and Mode...read more

Conditionals are statements in programming that allow for different actions to be taken based on whether a certain condition is true or false.

• Conditionals are used to make decisions in code based on specified conditions.

• They typically involve if-else statements or switch-case statements.

• Examples include if (condition) { // do something } else { // do something else }

• Another example is switch (variable) { case value1: // do something; break; case value2: // do something else; ...read more

if let unwraps an optional value if it exists, guard statement unwraps an optional value and exits the scope if it doesn't exist

• if let is used to safely unwrap an optional value and assign it to a new variable within the scope

• guard statement is used to unwrap an optional value and ensure it exists for the rest of the scope, otherwise it exits the scope

• if let example: if let name = optionalName { print(name) }

• guard example: guard let age = optionalAge else { return }

I have used MVC, MVVM, and VIPER architectures in iOS development.

• MVC (Model-View-Controller): Separates data, presentation, and user interaction.

• MVVM (Model-View-ViewModel): Enhances separation of concerns and testability.

• VIPER (View-Interactor-Presenter-Entity-Routing): Provides clear separation of components.

Environmental objects refer to physical entities in the environment that can be interacted with or manipulated by the user or application.

• Environmental objects can include items like trees, buildings, vehicles, and furniture in a virtual reality environment.

• These objects can be programmed to have specific behaviors or properties, such as collision detection or physics simulations.

• Interacting with environmental objects can enhance user immersion and engagement in the virtual e...read more

MVC architecture is a design pattern used in software development to separate the application into three main components: Model, View, and Controller.

• Model represents the data and business logic of the application.

• View is responsible for displaying the data to the user.

• Controller acts as an intermediary between Model and View, handling user input and updating the Model accordingly.

• MVC helps in organizing code, improving maintainability, and promoting reusability.

• Examples of M...read more

Retain cycle occurs when two objects hold a strong reference to each other, preventing them from being deallocated.

• Occurs in iOS development when two objects have strong references to each other

• Can lead to memory leaks as the objects are never deallocated

• Prevented by using weak or unowned references in Swift

Local data is managed using Core Data framework in iOS development.

• Use Core Data framework to create, read, update, and delete local data.

• Utilize entities, attributes, and relationships to model the data.

• Implement fetch requests to retrieve data based on specific criteria.

• Use NSManagedObject subclasses to represent data objects.

• Utilize NSPersistentContainer to manage the Core Data stack.

Protocol Oriented Programming is a programming paradigm in Swift that focuses on defining protocols to define behavior.

• POP is a way of designing code by defining protocols that describe a set of behaviors.

• It encourages composition over inheritance, allowing for more flexible and reusable code.

• By using protocols, you can define a blueprint of methods and properties that a type must implement.

GCD (Grand Central Dispatch) is a concurrency framework that allows developers to perform tasks asynchronously.

• GCD is used to manage concurrent operations in iOS apps.

• It uses dispatch queues to manage tasks and execute them in parallel.

• GCD provides different types of queues such as serial, concurrent, and main queues.

• Example: DispatchQueue.main.async { // code to be executed on main queue }

• Example: DispatchQueue.global(qos: .userInitiated).async { // code to be executed on a ...read more

Protocols in iOS are a set of rules that define methods and properties that a class must implement.

• Protocols are similar to interfaces in other programming languages.

• They allow for communication between classes that may not have a direct relationship.

• Classes, structs, and enums can adopt protocols.

• Example: UITableViewDelegate protocol is adopted by classes to handle table view data and interactions.

Generics in Swift allow you to write flexible, reusable functions and types that can work with any type.

• Generics enable you to write functions and types that can work with any type.

• They help in writing flexible and reusable code.

• Example: Array can hold elements of any type T.

To push an app on the Apple store, you need to create an Apple Developer account, prepare your app for submission, submit it for review, and then release it to the store.

• Create an Apple Developer account

• Prepare your app for submission by following Apple's guidelines

• Submit your app for review through the App Store Connect portal

• Wait for Apple to review your app and provide feedback

• Once approved, release your app to the Apple store for users to download

Table view displays data in a single column, while collection view allows for more complex layouts with multiple columns and rows.

• Table view is typically used for displaying lists of data in a single column.

• Collection view allows for more flexibility in layout, with support for multiple columns and rows.

• Collection view can also display data in a grid layout, while table view is limited to a single column.

• Table view is more suitable for simple, linear data presentation, while ...read more

MVVM is an architectural design pattern that separates the user interface code from the business logic and data model.

• MVVM stands for Model-View-ViewModel

• Model represents the data and business logic

• View displays the UI elements and interacts with the user

• ViewModel acts as a mediator between the Model and View, handling user inputs and updating the Model

• MVVM helps in achieving separation of concerns and making the code more modular and testable

Serialisation in API is the process of converting data into a format that can be easily transmitted over a network.

• Serialisation is used to convert complex data structures into a format that can be easily transmitted over a network.

• It involves converting objects or data structures into a stream of bytes that can be sent over a network.

• JSON and XML are commonly used formats for serialising data in APIs.

• Serialisation is important for ensuring data consistency and interoperabili...read more

The application lifecycle inside app delegate manages the state transitions of the app.

• The app delegate methods like applicationDidFinishLaunching, applicationWillResignActive, applicationDidEnterBackground, applicationWillEnterForeground, applicationWillTerminate, etc. handle different states of the app.

• These methods are called by the system at specific points during the app's lifecycle.

• Developers can use these methods to perform tasks like initializing app data, saving stat...read more

Best practices for handling memory leaks in iOS development

• Use Instruments to identify memory leaks

• Avoid strong reference cycles with weak or unowned references

• Use autorelease pools for temporary objects

• Implement proper memory management with ARC (Automatic Reference Counting)

Delegate pattern is a design pattern in which an object delegates some of its responsibilities to another object.

• Create a protocol defining the methods that the delegate should implement

• Declare a delegate property in the delegating class

• Set the delegate property to the object that will act as the delegate

• Call the delegate methods from the delegating class

The architecture of an iOS app refers to the overall structure and organization of its code.

• iOS apps typically follow the Model-View-Controller (MVC) architecture pattern.

• The Model represents the data and business logic, the View displays the user interface, and the Controller manages the interactions between the Model and View.

• Other popular architecture patterns for iOS apps include VIPER, MVVM, and Clean Architecture.

• Choosing the right architecture depends on the specific n...read more

I follow the MVC (Model-View-Controller) design pattern in my iOS development.

• Separates data (Model), user interface (View), and control logic (Controller)

• Improves code organization and maintainability

• Promotes reusability and scalability

• Examples: UIKit framework in iOS uses MVC pattern

Swift is a modern, fast, and safe programming language developed by Apple, while Objective-C is an older, more verbose language.

• Swift is more concise and easier to read than Objective-C.

• Swift supports optionals and type inference, making code safer and less prone to errors.

• Objective-C requires manual memory management with retain and release, while Swift uses automatic reference counting (ARC).

• Swift is interoperable with Objective-C, allowing developers to use both languages ...read more

Encapsulation is the concept of bundling data and methods that operate on the data into a single unit.

• Encapsulation helps in hiding the internal state of an object and restricting access to it.

• It allows for better control over the data by preventing outside code from directly accessing it.

• Encapsulation also helps in achieving data abstraction, where the internal details of an object are hidden and only the necessary information is exposed to the outside world.

Real-time chat can be stored using a database or cloud storage service.

• Choose a database or cloud storage service that suits your app's needs.

• Design a schema to store chat messages and related metadata.

• Implement CRUD operations to create, read, update, and delete chat messages.

• Consider using encryption and access controls to protect user data.

• Test and optimize the storage solution for performance and scalability.

Publishers work by creating, distributing, and monetizing content through various channels.

• Publishers create content such as articles, videos, or apps.

• They distribute the content through platforms like websites, social media, or app stores.

• Publishers monetize their content through advertising, subscriptions, or in-app purchases.

SwiftUI is a user interface toolkit introduced by Apple for building apps across all Apple platforms using Swift programming language.

• Declarative syntax for building user interfaces

• Works seamlessly with Swift code

• Supports dynamic type, dark mode, localization, and accessibility

• Live preview feature for real-time UI updates

• Integrates with existing UIKit and AppKit views

Combine is a framework introduced by Apple for processing values over time.

• Combine is used for handling asynchronous events and data streams in Swift.

• It provides a declarative Swift API for processing values over time.

• Combine can be used for tasks like responding to user input, network requests, and more.

• It allows developers to work with asynchronous data streams in a more functional and reactive way.

• Example: Using Combine to handle network requests and update UI based on the...read more

Frame and bound are properties used in iOS development to define the position and size of a view within its superview.

• Frame refers to the view's position and size in its superview's coordinate system.

• Bound refers to the view's position and size in its own coordinate system, relative to its own top-left corner.

• Changing the frame will move the view within its superview, while changing the bound will not affect its position but may affect its content layout.

Struct and class are both used to define custom data types in Swift, but they have some key differences.

• Struct is a value type, while class is a reference type

• Structs are passed by value, while classes are passed by reference

• Classes support inheritance, while structs do not

• Classes have deinitializers, while structs do not

• Classes can have reference counting for memory management, while structs do not

Program to create a triangle using asterisks

• Use nested loops to print each row of the triangle

• Increment the number of asterisks printed in each row

• Example: for a triangle with 5 rows, the output would be: * , ** , *** , **** , *****

Generics in Swift allow you to write flexible, reusable functions and types that can work with any type.

• Generics enable you to write functions and types that can work with any type, without specifying the actual type.

• They help in writing flexible and reusable code.

• Example: Array is a generic type in Swift that can hold elements of any type T.

Classes are reference types, while structs are value types in Swift.

• Classes are reference types, meaning they point to the same memory location when assigned to a new variable.

• Structs are value types, meaning they create a new copy when assigned to a new variable.

• Classes support inheritance, while structs do not.

• Classes can have deinitializers, while structs cannot.

• Example: class Person {} vs struct Point {}

GCD (Grand Central Dispatch) is a technology in Swift for managing concurrent operations.

• GCD is used for managing concurrent tasks in iOS applications.

• It provides a way to perform tasks in the background without blocking the main thread.

• GCD uses queues to schedule tasks for execution.

• Example: DispatchQueue.main.async { // code to run on the main thread }

Autoclosure is a feature in Swift that automatically wraps an expression in a closure.

• Autoclosure is used to delay evaluation of an expression until it is actually needed.

• It is commonly used with functions that take closures as arguments, allowing the caller to pass in a regular value instead of a closure.

• Autoclosures are created by adding @autoclosure attribute before the closure's parameter type.