80+ Senior IOS Developer Interview Questions and Answers

MVC focuses on separating data, presentation, and logic, while MVVM adds a ViewModel layer to enhance data binding and separation of concerns.

• MVC: Model-View-Controller pattern separates data, presentation, and logic. Views directly interact with Models and Controllers.

• MVVM: Model-View-ViewModel pattern adds a ViewModel layer between the View and Model to enhance data binding and separation of concerns.

• MVC is more traditional and widely used, while MVVM is gaining popularity ...read more

Classes are reference types, while structs are value types. Classes are used for complex data structures, inheritance, and reference counting. Structs are used for simple data types and performance optimization.

• Classes are reference types, stored on the heap, and support inheritance and reference counting. Use classes for complex data structures like objects, where identity matters.

• Structs are value types, stored on the stack, and do not support inheritance. Use structs for s...read more

Key principles of memory management in iOS app development include reference counting, autorelease pools, and avoiding retain cycles.

• Use ARC (Automatic Reference Counting) to manage memory automatically

• Avoid retain cycles by using weak references or unowned references

• Use autorelease pools to manage memory for temporary objects

Create a modular iOS app with SwiftUI, async/await, and unit tests using a provided API.

• Use SwiftUI for UI components: Create a List view for the listings screen and a Detail view for individual items.

• Implement async/await for API calls: Use URLSession to fetch data from the fake-json API asynchronously.

• Apply Combine for reactive programming: Use Combine to handle data streams and updates in the UI.

• Utilize Dependency Injection: Pass dependencies (like API clients) through ini...read more

System design for a food delivery app like Zomato

• Identify user roles: customers, restaurants, delivery partners

• Design a database schema to store user information, orders, menus, etc.

• Implement a search feature to find restaurants based on location, cuisine, etc.

• Integrate payment gateway for secure transactions

• Develop a user-friendly interface for placing orders and tracking delivery status

• Implement push notifications for order updates and promotions

• Ensure scalability and relia...read more

Integrating and maintaining third-party libraries involves adding dependencies, managing versions, and updating as needed.

• Use dependency management tools like CocoaPods or Carthage to easily add and update libraries

• Regularly check for updates and security patches for third-party libraries

• Ensure compatibility with existing codebase by testing thoroughly after integrating new libraries

State object is a specific instance of a state, while state is a general concept representing the condition of a system.

• State object is a concrete representation of a state in a program, containing specific values and properties.

• State is an abstract concept that defines the overall condition or status of a system.

• In iOS development, state object could refer to an instance of a class representing the current state of a view or component.

• State, on the other hand, could refer to...read more

UITableView for displaying data in a list format, UICollectionView for displaying data in a grid or custom layout.

• Use UITableView for displaying data in a list format, such as a contact list or a news feed.

• Use UICollectionView for displaying data in a grid or custom layout, such as a photo gallery or a calendar.

• UITableView is simpler to implement and more efficient for displaying large amounts of data.

• UICollectionView offers more flexibility in terms of layout and customizati...read more

1. Atomic properties ensure that the value is always fully retrieved or set, while nonatomic properties do not guarantee this. 2. Memory management in Swift is handled automatically using Automatic Reference Counting (ARC). 3. Classes are reference types, while structs are value types in Swift. 4. Factorial pattern is a design pattern used to calculate the factorial of a number.

• Atomic properties ensure thread safety by ensuring that the value is fully retrieved or set before ...read more

Debouncing technique in Swift is used to limit the rate at which a function is called, preventing it from being called multiple times in a short period.

• Debouncing involves setting a time threshold and only allowing the function to be called after that threshold has passed without any new calls.

• It is commonly used in scenarios like search bars or buttons to prevent rapid firing of events.

• Example: Implementing a search functionality where the search query is only executed after...read more

Swift is a modern programming language for iOS development, while Objective-C is an older language with a different syntax and runtime.

• Syntax: Swift has a more concise and readable syntax compared to Objective-C, which uses a more verbose syntax with square brackets for method calls. Example: Swift uses 'let x = 10' while Objective-C uses 'NSNumber *x = [NSNumber numberWithInt:10];'.

• Memory Management: Swift uses Automatic Reference Counting (ARC) for memory management, while ...read more

I have worked on MVVM architecture in my previous project.

• MVVM stands for Model-View-ViewModel.

• It separates the UI logic from the business logic.

• The View interacts with the ViewModel, which in turn interacts with the Model.

• I used RxSwift for binding the ViewModel and View in my previous project.

ARC stands for Automatic Reference Counting, a memory management system used in iOS development.

• ARC automatically tracks and manages the memory used by objects in an iOS application.

• It adds and removes references to objects based on their usage, ensuring memory is properly managed.

• ARC helps prevent memory leaks and retains cycles by automatically releasing objects when they are no longer needed.

Static variables in Swift are used when you want to maintain a single instance of a variable across all instances of a class or struct.

• Used to store values that are common to all instances of a class or struct

• Can be accessed without creating an instance of the class or struct

• Helpful for maintaining state across multiple instances

Answers to questions related to IOS development concepts.

• Delegate and protocol are used for communication between objects in IOS. Delegate is a design pattern that allows one object to send messages to another object when a specific event occurs. Protocol is a set of methods that a class can implement to provide a specific behavior.

• MVC is a design pattern used in IOS development. It separates the application into three components: Model, View, and Controller. Model represents...read more

Real time data in mobile apps can be handled using technologies like WebSockets, Firebase Realtime Database, or Push Notifications.

• Use WebSockets for bidirectional communication between client and server.

• Utilize Firebase Realtime Database for syncing data in real time across devices.

• Implement Push Notifications to notify users of real time updates even when the app is not open.

I use Xcode Instruments regularly to analyze app performance and memory usage.

• I use Xcode Instruments to identify memory leaks and optimize app performance.

• I use it to analyze CPU and memory usage during app execution.

• I also use it to profile network activity and identify any bottlenecks.

• Xcode Instruments helps me identify areas for improvement in app code and performance.

• For example, I use the Time Profiler instrument to analyze CPU usage and optimize code execution.

Collections are data structures that store and organize multiple objects or values.

• Collections are used to group related data together.

• They provide methods for adding, removing, and accessing elements.

• Examples of collections in iOS include arrays, sets, and dictionaries.

OOPS (Object-Oriented Programming) is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.

• OOPS focuses on creating objects that interact with each other to solve a problem.

• It involves concepts like Inheritance, Encapsulation, Polymorphism, and Abstraction.

• Inheritance allows a class to inherit properties and behavior from another class.

• Encapsulation involves bundling data and methods that opera...read more

To fix a crash in an application, identify the root cause, analyze crash logs, use debugging tools, and test the fix thoroughly.

• Identify the root cause of the crash by analyzing crash logs and user reports.

• Use debugging tools like Xcode's debugger or third-party tools like Crashlytics.

• Implement defensive coding practices to handle edge cases and prevent crashes.

• Test the fix thoroughly on different devices and iOS versions to ensure stability.

• Consider using automated testing t...read more

A protocol extension allows adding functionality to existing types without modifying their original implementation.

• Define a protocol with required methods

• Create an extension for the protocol

• Implement the methods in the extension

MVVM is a design pattern that separates the UI from the business logic by introducing a middle layer called ViewModel.

• Model-View-ViewModel design pattern

• ViewModel acts as a link between the Model and View

• Data binding is used to connect the ViewModel to the View

• Updates in the ViewModel automatically reflect in the View

Lazy property delays the initialization of a property until it is accessed for the first time.

• Lazy properties are useful when the initialization of a property is expensive and not always needed.

• They can improve performance and memory usage by delaying the initialization until it is actually needed.

• They are declared using the 'lazy' keyword and must be variables, not constants.

• Example: lazy var myProperty = expensiveInitialization()

• Lazy properties are thread-safe by default in...read more

Experienced iOS developer with a strong background in building scalable applications and overcoming technical challenges.

• Led a team to develop a telemedicine app, improving patient-doctor communication.

• Implemented Core Data for offline data storage, enhancing user experience.

• Faced challenges with integrating third-party APIs, resolved by creating custom wrappers.

• Optimized app performance, reducing load time by 30% through code refactoring.

• Collaborated with UX designers to imp...read more

Memory management in iOS involves managing memory allocation, deallocation, and optimization to prevent memory leaks and crashes.

• Use ARC (Automatic Reference Counting) to automatically manage memory by tracking references to objects

• Avoid retain cycles by using weak references or unowned references

• Use instruments like Xcode's Memory Graph Debugger to analyze memory usage and identify leaks

• Release unnecessary objects and resources to free up memory

Memory leak is a situation where a program fails to release memory it has allocated, leading to a gradual loss of available memory.

• Memory leaks occur when a program allocates memory but does not free it after use.

• Common causes of memory leaks include not deallocating memory after use, retaining references to objects unnecessarily, and circular references.

• To solve memory leaks, developers can use tools like Instruments to identify leaks, analyze code for potential issues, and ...read more

OOPS stands for Object-Oriented Programming System. There are four main types of OOPS concepts: Inheritance, Encapsulation, Polymorphism, and Abstraction.

• Inheritance: Allows a class to inherit properties and behavior from another class. Example: class B extends class A.

• Encapsulation: Bundling data and methods that operate on the data into a single unit. Example: private variables in a class.

• Polymorphism: Ability to present the same interface for different data types. Example:...read more