iOS development is a critical field that shapes user experience within the Apple ecosystem. In interviews for iOS developer positions, candidates are rigorously assessed on their knowledge of Swift/Objective-C, proficiency in UIKit/SwiftUI, and their understanding of Apple’s development principles.

In this article, we have compiled 10 essential questions you may encounter at both junior and senior levels during iOS developer interviews, along with sample answers.

This guide will help you test your technical knowledge while preparing for iOS developer interviews. Keep reading for tips that will help you stand out as an iOS developer!

1. What Are the Key Differences Between Swift and Objective-C?

Swift and Objective-C are the two main programming languages Apple offers for iOS development.

This question is asked to evaluate the reasoning behind your language preference:

Swift:

• Modern, safe, and readable.
• Features such as Optionals, type inference, and memory management (ARC).
• Offers less code writing and easier debugging.

Objective-C:

• C-based syntax with dynamic runtime features.
• Still used in older projects, especially in large enterprise applications.
• Features like categories and message passing.
   

Preference Reasoning: Swift is preferred for new projects due to Apple's official support and modern features, while knowledge of Objective-C may be necessary for older projects.

2. What is the Optional Concept, and How Does Nil Coalescing Work?

Optionals are a frequently questioned topic in Swift during interviews.

Optional: Indicates whether a variable has a value or not.

Example:
var name: String?
This means the name variable could be nil.

Nil Coalescing: Used to unwrap Optionals.

Example:
let username = enteredName ?? "Guest"
This code uses "Guest" if enteredName is nil.

3. Compare the MVC and MVVM Architectural Patterns

Architectural patterns are crucial for code organization in iOS projects.

MVC (Model-View-Controller):

• Apple’s traditional architectural approach.
• Clearly separates the Controller, View, and Model.
• However, it can lead to the "Massive View Controller" problem.
   

MVVM (Model-View-ViewModel):

• Reduces the dependency between the View and Model.
• Compatible with reactive programming (Combine, RxSwift).
• Enables more modular and testable code.
   

Preference: MVVM is recommended for large projects, while MVC might suffice for smaller projects.

4. How Does ARC (Automatic Reference Counting) Work?

Memory management is an important topic in iOS interviews.

ARC (Automatic Reference Counting):

• Automates memory management through reference counting.
• Automatically cleans up unused objects.
   

Retain Cycle:

Occurs when two objects reference each other strongly.

Solution: Use weak or unowned references.

class Person {
   weak var apartment: Apartment?
}

5. What Are the Differences Between UIKit and SwiftUI?

Apple’s UI frameworks are foundational for iOS developers.

UIKit:

• A traditional, imperative approach.
• Used with Storyboards or programmatically-created UI.
• ViewController-based and requires more boilerplate code.
   

SwiftUI:

• A declarative structure.
• Compatible with iOS 13+ and allows rapid prototyping.
• Offers less code and a more readable structure.

Preference: SwiftUI is used for new projects, while UIKit is employed in older projects.

6. What is the Delegation Pattern?

Delegation is a commonly used pattern in iOS development.

Purpose: To delegate the functionality of one object to another object.

Example:

class ViewController: UIViewController, UITableViewDelegate {
   func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
       print("Row selected: \(indexPath.row)")
   }
}

7. How Are Asynchronous Operations Managed Using Grand Central Dispatch (GCD)?

DispatchQueue: Executes tasks on either the main or background threads.

Example:

DispatchQueue.global(qos: .background).async {
   // Background task
   DispatchQueue.main.async {
       // UI update
   }
}

8. What Are the Differences Between Core Data and Realm?

Data storage solutions are a common interview topic in iOS development.

Core Data:

• Apple’s official solution.
• Based on SQLite and can manage complex relationships.

Realm:

• A third-party library.
• Faster and easier to use.

9. How Do You Write Unit Tests and UI Tests?

Unit Test:

• Tests the functional logic.
• Written with the XCTest framework.
   

UI Test:

• Simulates user interface flows.
• Written using XCUITest.

10. How Does the App Store Submission Process Work?

Apple’s submission process is often tested for practical knowledge in interviews.

Required Steps:

• Developer Account: Requires an annual paid account.
• Provisioning Profiles and Certificates: Used to sign the app.
• App Store Connect: Upload metadata and screenshots.

Conclusion

iOS interview questions are designed to assess your technical knowledge and problem-solving skills. In this guide, we have covered critical topics such as Swift, UIKit, and Apple’s ecosystem, along with common interview questions and answers.

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