Top 35+ iOS Interview Questions: What to Expect and How to Respond

Automatic Reference Counting (ARC) is a memory management system in iOS. It automatically tracks and manages memory, preventing memory leaks and enhancing overall app performance. 

A Bundle ID is a unique identifier for an iOS app that is crucial for app distribution, push notifications, and security. 

iOS follows a layered architecture with Cocoa Touch, Media, Core Services, and Core OS, each serving specific purposes in app development. 

Objective-C supports various data types, including int, float, double, char, BOOL, NSArray, NSDictionary, and NSString. 

Cocoa is a general framework, while Cocoa Touch is tailored for touch-based interactions on iOS devices, providing essential classes for app development. 

Objective-C and Swift are the main languages for iOS development, with Swift gaining popularity for its modern features. 

Concurrency in iOS can be achieved through threads, Grand Central Dispatch (GCD), and Operation Queues. 

iOS is exclusive to Apple devices, has a closed ecosystem, and uses Xcode with Swift or Objective-C. Android is open-source, supports various devices, and uses Java or Kotlin. 

Atomic properties provide thread safety, while nonatomic properties are faster but don't guarantee thread safety. 

An app is not running when it has not been launched or terminated by the system. 

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In iOS, an object is an instance of a class that encapsulates data and behaviour, forming the foundation of an app. 

An app is in an active state when running in the foreground, receiving user input, and fully operational. 

The UIKit framework is used to build an iOS application's user interface, offering essential UI development components. 

iBeacon, developed by Apple, uses BLE to enable location-based services in iOS, facilitating features like proximity-based notifications. 

Method Swizzling involves swapping method implementations at runtime and is used for extending or modifying class behaviour without subclassing. 

A category in iOS programming adds methods to an existing class, aiding code organisation and extending functionalities. 

ViewDidLoad is called when a view is loaded into memory, while ViewDidAppear is named after the view is presented on the screen. ViewDidLoad is used for one-time setup, and ViewDidAppear for actions upon every appearance. 

Key-Value Observing (KVO) allows objects to observe changes to a property of another object, facilitating reactive programming patterns. 

Layer objects, represented by CALayer, manage visual content, render on the screen, and support animations. 

In Xcode, "Targets" group-related files and "File Types" categorise files based on types, aiding organisations. 

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Access the Code Snippet Library in Xcode using the "Code Snippet Library" button in the code editor's toolbar, offering reusable code snippets. 

TVMLKit is a framework for building Apple TV app interfaces using TVML (TV Markup Language), enhancing user experiences on the big screen. 

Grand Central Dispatch (GCD) is an iOS API managing concurrent operations by providing a high-level interface for task execution. 

iOS 14 introduced features such as the App Library, home screen widgets, App Clips, and enhanced privacy settings. 

Concurrency in iOS is achieved through threads, GCD, and Operation Queues, offering various levels of control and abstraction. 

The viewDidLoad method is commonly used for final setup and initialisation before displaying the app to the user. 

Code Coverage in iOS development measures the percentage of code tested by automated tests, aiding developers in assessing test thoroughness. 

The Responder Chain is a series of objects in iOS that respond to events, facilitating the handling of user interactions. 

Operator Overloading in Swift allows developers to define custom implementations for standard operators, enhancing code readability. 

Design patterns enhance code maintainability, scalability, and readability in iOS development, with Model, View, and Controller (MVC) and Model-View ViewModel (MVVM) commonly used patterns. 

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The Adapter Pattern allows an existing class interface to be used as another interface, ensuring compatibility when integrating new components or libraries.

In iOS, "assign" is used for primary data types, while "retain" is used for object types, retaining ownership and preventing premature deallocation. 

Key-Value Coding (KVC) is for dynamically accessing an object's properties, while Key-Value Observing (KVO) is for notifying changes in specific properties in other objects. 

The Observer Pattern facilitates reactive programming, where an object (subject) maintains a list of dependents (observers) that are notified and updated upon changes. 

Realm, a mobile database, offers simplicity, speed, and support for live objects in iOS development, making it a preferred choice for developers. 

The "codable protocol" is commonly used for JSON data handling in iOS, providing easy encoding and decoding of Swift types. 

For efficient location tracking in iOS, developers use Core Location, specifically CLLocationManager, and APIs like Significant-Change Location Service and Region Monitoring to minimise power consumption