200+ IOS Developer Interview Questions and Answers

Memory management in iOS uses ARC to manage object lifetimes and avoid retain cycles with weak references.

• iOS uses Automatic Reference Counting (ARC) to manage memory automatically.

• ARC keeps track of strong references to objects and deallocates them when no strong references remain.

• Retain cycles occur when two objects hold strong references to each other, preventing deallocation.

• To avoid retain cycles, use 'weak' or 'unowned' references in closures or delegate patterns.

• Exampl...read more

Add two numbers represented by linked lists in reverse order.

• Traverse both linked lists simultaneously, adding corresponding nodes and carrying over the sum if necessary.

• Handle cases where one linked list is longer than the other.

• Create a dummy head node to simplify the code.

• Consider edge cases like carry over at the end of the addition.

Race condition occurs when multiple threads access shared data and try to change it at the same time. Data race is a type of race condition where two or more threads access shared data and at least one of them modifies it.

• Race condition occurs when multiple threads access shared data and try to change it at the same time.

• Data race is a type of race condition where two or more threads access shared data and at least one of them modifies it.

• Race conditions can lead to unpredict...read more

MVC focuses on separation of concerns, while MVP focuses on the interaction between components.

• MVC stands for Model-View-Controller, where the controller handles user input, the model manages the data, and the view displays the data.

• MVP stands for Model-View-Presenter, where the presenter acts as an intermediary between the model and the view, handling user input and updating the view.

• In MVC, the view has direct access to the model, while in MVP, the presenter mediates the co...read more

MVC architecture in iOS separates app logic into Model, View, and Controller for better organization and maintainability.

• Model: Represents data and business logic. Example: A 'User' class that handles user data.

• View: The user interface elements. Example: Storyboards and UI components like buttons and labels.

• Controller: Manages the interaction between Model and View. Example: A 'UserViewController' that updates the UI based on user data.

Synchronous operations block execution until complete; asynchronous allows other tasks to run while waiting for completion.

• Synchronous: Code execution waits for a task to finish before moving to the next line.

• Asynchronous: Code execution continues without waiting for the task to finish.

• Example of synchronous: A function that reads a file and returns its content before proceeding.

• Example of asynchronous: A network request that allows the app to remain responsive while waiting ...read more

iOS and Android apps differ in development environments, design guidelines, and user experience.

• Development Language: iOS uses Swift/Objective-C, while Android uses Java/Kotlin.

• User Interface: iOS follows Human Interface Guidelines; Android uses Material Design.

• App Distribution: iOS apps are distributed via the App Store; Android apps can be distributed through multiple platforms.

• Hardware Fragmentation: Android runs on various devices with different screen sizes and hardware;...read more

Types of memory management in iOS include Automatic Reference Counting (ARC) and Manual Reference Counting (MRC).

• Automatic Reference Counting (ARC) - manages memory automatically by keeping track of object references.

• Manual Reference Counting (MRC) - requires developers to manually manage memory by retaining and releasing objects.

• ARC is the default memory management system in iOS, while MRC is used in older codebases or when developers need more control over memory management...read more

The view controller lifecycle manages the creation, display, and destruction of view controllers in iOS apps.

• viewDidLoad: Called after the view controller has loaded its view hierarchy into memory. Example: Initialize UI elements here.

• viewWillAppear: Called just before the view appears on the screen. Example: Update UI based on data changes.

• viewDidAppear: Called after the view has appeared on the screen. Example: Start animations or data fetching.

• viewWillDisappear: Called jus...read more

I use GIT for version control and manage conflicts by resolving them through communication and collaboration.

• Regularly commit changes to keep track of progress

• Pull latest changes before making any updates to avoid conflicts

• Communicate with team members to resolve conflicts efficiently

• Use tools like Git merge or Git rebase to resolve conflicts

• Document resolution process for future reference

GCD and Operation Queues are both used for concurrent programming in iOS, but differ in their approach.

• GCD is a C-based API that uses a thread pool model for concurrency.

• Operation Queues are built on top of GCD and provide a higher-level abstraction for concurrency.

• GCD is best for simple, lightweight tasks, while Operation Queues are better for more complex tasks with dependencies.

• GCD uses blocks for task execution, while Operation Queues use Operation objects.

• GCD has a lower...read more

Frameworks are single-platform libraries, while xcFrameworks support multiple platforms and architectures.

• Frameworks are typically built for a single platform (iOS, macOS, etc.).

• xcFrameworks can contain binaries for multiple platforms (iOS, macOS, tvOS, watchOS).

• Frameworks are distributed as a single .framework bundle, while xcFrameworks are distributed as a .xcframework bundle.

• Example: A standard Framework might be used for an iOS app, while an xcFramework can be used for bo...read more

Classes are reference types while structs are value types.

• Classes are passed by reference while structs are passed by value.

• Classes support inheritance while structs do not.

• Classes have a default initializer while structs do not.

• Classes can be deinitialized while structs cannot.

• Examples of classes include UIView and UIViewController while examples of structs include CGRect and CGPoint.

View Controllers manage views and user interactions, while UIViews are the building blocks for the visual interface in iOS apps.

• View Controllers (e.g., UIViewController) manage the app's view hierarchy and handle user interactions.

• UIViews are the visual elements (e.g., UIButton, UILabel) that display content on the screen.

• A View Controller can contain multiple UIViews to create a complex interface.

• View Controllers handle lifecycle events (e.g., viewDidLoad, viewWillAppear) wh...read more

The interview question covers topics like solving two sum problems, NSOperation vs GCD, view life cycle, and tuples.

• Two sum problems involve finding two numbers in an array that add up to a specific target. Example: [2, 7, 11, 15], target = 9

• NSOperation and GCD are both used for concurrent programming in iOS. NSOperation provides more control and features, while GCD is lower level and more lightweight.

• View life cycle in iOS involves methods like viewDidLoad, viewWillAppear, v...read more

Delegates and notification center are key components in iOS development for communication between objects and broadcasting events.

• Delegates are used for one-to-one communication between objects, allowing one object to act on behalf of another.

• Notification center is used for broadcasting events to multiple objects, allowing for loosely coupled communication.

• Delegates are commonly used in UITableView and UICollectionView to handle data and user interactions.

• Notification center ...read more

A retain cycle in programming occurs when two objects hold a strong reference to each other, preventing them from being deallocated.

• Retain cycles can lead to memory leaks in iOS development.

• To break a retain cycle, one of the objects involved needs to have a weak reference to the other.

• An example of a retain cycle is when a parent object holds a strong reference to a child object, and the child object holds a strong reference back to the parent.

I was tasked with designing a user-friendly interface for a health tracking app, focusing on usability and aesthetics.

• Conducted user research to understand needs and preferences.

• Created wireframes and prototypes using tools like Sketch and Figma.

• Implemented a color scheme that promotes calmness and clarity.

• Ensured accessibility features were integrated for users with disabilities.

• Collaborated with developers to ensure smooth transitions and animations.

Use a Set to get distinct members in array while maintaining sequence.

• Iterate through the array and add each element to a Set to automatically remove duplicates.

• Create a new array by iterating through the Set to maintain the original sequence.

A string can form a palindrome if at most one character has an odd frequency.

• Count the frequency of each character in the string.

• A palindrome can have at most one character with an odd count.

• Example: 'civic' -> c:2, i:1, v:1 (valid, odd count for 'i' only)

• Example: 'ivicc' -> i:2, v:1, c:2 (valid, odd count for 'v' only)

• Example: 'hello' -> h:1, e:1, l:2, o:1 (invalid, multiple odd counts)

Types of access controls in iOS include public, internal, private, and fileprivate.

• Public: Accessible from anywhere, both within the module and outside.

• Internal: Accessible from anywhere within the module.

• Private: Accessible only within the defining type.

• Fileprivate: Accessible only within the same file.

ARC stands for Automatic Reference Counting. It is a memory management system used in Swift to automatically manage memory allocation and deallocation.

• ARC automatically tracks and manages the memory used by objects in Swift.

• It keeps track of how many references to an object exist and deallocates the object when there are no more references to it.

• ARC eliminates the need for manual memory management, reducing the risk of memory leaks and crashes.

• Developers don't need to explici...read more

Swift 5 introduced ABI stability, improved performance, and new language features.

• ABI stability ensures compatibility between future Swift versions

• Improved performance with faster build times and reduced app size

• New language features include Result type, Raw strings, and Property wrappers

Sorting without higher order functions and remote notifications

• Implement sorting algorithm like bubble sort, selection sort, or insertion sort without using built-in sort functions

• For remote notifications, use Apple Push Notification Service (APNs) to send notifications to users' devices

ARC (Automatic Reference Counting) is a memory management mechanism in Swift that automatically manages memory by keeping track of references to objects.

• ARC automatically deallocates objects when they are no longer referenced

• Retain cycles can occur if two objects hold strong references to each other

• Weak and unowned references are used to prevent retain cycles

I primarily use UIKit and SwiftUI frameworks for iOS development projects.

• Primary frameworks: UIKit, SwiftUI

• Additional frameworks: Core Data, Core Animation

• Examples: UIKit for building user interfaces, SwiftUI for declarative UI design

Memory management in iOS involves automatic reference counting (ARC) and manual techniques to optimize resource usage.

• Automatic Reference Counting (ARC) manages memory automatically by keeping track of object references.

• Use weak references to avoid retain cycles, especially in closures and delegate patterns. Example: 'weak var delegate: MyDelegate?'

• Utilize 'autorelease pools' to manage temporary objects and release memory when no longer needed.

• Profile memory usage with Instru...read more