What Are Common iOS Interview Questions and How Should You Answer Them?

Understanding common iOS interview questions and preparing structured answers significantly increases your chances of hiring success. This guide analyzes eight technical questions, providing sample answers and insight into what recruiters assess. Based on our assessment experience, mastering these topics demonstrates core competency in Swift, application architecture, and iOS-specific frameworks.

What Are the Key iOS Application States and Their Lifecycle?

Recruiters use this question to evaluate your foundational understanding of the iOS application lifecycle. A clear explanation shows you can develop responsive apps that handle background tasks and state transitions smoothly. The application state refers to the various stages an app goes through during user interaction and system events.

The primary states are:

• Not Running: The app has not been launched or was terminated by the system or user.
• Inactive: The app is running in the foreground but is not receiving events (e.g., during an incoming phone call or when a system alert appears).
• Active: The app is running in the foreground and is actively receiving user interactions.
• Background: The app is in the background but is still executing code. This is typical for tasks needing a few seconds to complete, like saving user data.
• Suspended: The app is in the memory but is not executing any code. The system may purge suspended apps to free up resources without notifying the user.

How Do You Differentiate Between an App ID and a Bundle ID?

This question tests your knowledge of app identity and distribution on the App Store. The Bundle ID is a unique identifier string in reverse DNS format (e.g., com.ok.YourAppName) that differentiates your app from all others on a device. It is specified in your Xcode project and is immutable.

In contrast, the App ID is configured in the Apple Developer Portal and is used to link your application to its provisioning profile and enabled app services (like Push Notifications or iCloud). While the App ID contains the Bundle ID, it also includes a Team ID and configures capabilities that allow your app to function correctly when distributed.

Can You Explain How iBeacon Technology Works?

Here, interviewers assess your knowledge of iOS-specific technologies like Bluetooth Low Energy (BLE). iBeacon is an Apple protocol that allows iOS devices to detect their precise location relative to a small, physical beacon transmitter. The beacon broadcasts a signal containing a unique identifier. When an iOS device with your app enters the beacon's proximity, it can trigger location-based actions, such as displaying a coupon in a retail store or providing navigation in a museum. This demonstrates your ability to implement context-aware features.

What Is the Model-View-Controller (MVC) Pattern in iOS?

Your answer reveals your architectural skills. MVC is a design pattern that separates an application into three components:

• Model: Manages the app’s data and business logic (e.g., data structures, database interactions).
• View: Represents the user interface elements (e.g., buttons, labels) that are built using UI frameworks like UIKit or SwiftUI.
• Controller (UIViewController): Acts as an intermediary. It processes user input from the View, updates the Model, and reflects changes back to the View.

Mastering MVC is crucial for writing organized, maintainable, and scalable code, a key skill recruiters seek.

Which Programming Languages Are Essential for iOS Development?

This question directly evaluates your technical toolkit. While several languages can be used, the two primary ones are:

• Swift: The modern, open-source language preferred by Apple and the industry. It offers safety features, performance benefits, and is more intuitive than its predecessor.
• Objective-C: The legacy language that is still found in many older codebases. Knowledge of it is valuable for maintaining existing projects.

Hiring managers want to see proficiency in Swift and an understanding of when Objective-C might be necessary.

To prepare effectively, candidates should: practice coding challenges, review core frameworks like UIKit and SwiftUI, and be ready to discuss their past projects in detail. Understanding the reasoning behind these questions allows you to demonstrate not just knowledge, but also problem-solving ability and a passion for iOS development.