Question 1

What is the difference between 'let' and 'var' in Swift?

Accepted Answer

let declares an immutable constant while var declares a mutable variable. A constant cannot be changed after declaration, but a variable can change value. Use let by default for safety and code clarity.

Question 2

What is an Array in Swift?

Accepted Answer

Array is an ordered collection storing elements of the same type and allowing duplicates. Elements are accessible by index starting from 0. Array maintains insertion order and suits scenarios where element order matters.

Question 3

What is a UIView?

Accepted Answer

UIView is the base class for all visual components in UIKit. It handles on-screen rendering, touch interactions, and view hierarchy. Every user interface in an iOS application relies on this fundamental class to structure and display content.

Question 4

What is the loadView method in the UIViewController lifecycle?

Accepted Answer

loadView is called to create the controller's root view. It is invoked before viewDidLoad and should only be overridden if the view is created programmatically without Interface Builder. It is the first stage of the lifecycle, ideal for building the root view hierarchy. Never call super.loadView() when overriding as it would load the default xib/storyboard.

Question 5

Which property wrapper to use for managing local state in a SwiftUI view?

Accepted Answer

@State creates a source of truth for mutable data within a view. SwiftUI automatically manages the lifecycle and redraws when the value changes. This is the fundamental mechanism for local state modifications in a single view.

Question 6

What is the main difference between NavigationStack and NavigationView in SwiftUI?

Accepted Answer

NavigationStack (iOS 16+) replaces NavigationView and provides explicit state management with NavigationPath. NavigationView uses an implicit navigation stack, while NavigationStack enables full programmatic control of navigation through bindable state.

Question 7

What is the main difference between URLSession.shared and a custom URLSession instance?

Accepted Answer

URLSession.shared is a global singleton with default configuration, ideal for simple requests. A custom instance allows configuring behavior (timeouts, caching, delegates) for specific needs. Using a custom instance provides fine-grained control over cache policies, SSL certificates, and redirections.

Question 8

What is ARC (Automatic Reference Counting) in iOS?

Accepted Answer

ARC is an automatic memory management mechanism that counts references to objects. The compiler automatically inserts retain and release calls, eliminating manual memory management. When the reference count reaches zero, the object is deallocated. ARC significantly simplifies iOS programming by preventing common memory leaks.

Question 9

What is a Publisher in Combine?

Accepted Answer

A Publisher is a fundamental protocol in Combine that describes how a sequence of values can be delivered over time. It is responsible for emitting values or errors to subscribers that connect to it. Understanding this concept is essential for working with Combine, as all other framework elements depend on this publication model.

Question 10

What is an async function in Swift?

Accepted Answer

An async function is one that can suspend and resume without blocking the thread. It uses the async keyword to indicate it can await asynchronous operations with await. The Swift compiler automatically generates code to manage the suspension state, allowing other tasks to execute during waits.

Câu hỏi phỏng vấn iOS

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Khám phá tất cả chủ đề iOS

Swift Basics

Swift Language Essentials

UIKit Fundamentals

UIViewController Lifecycle

UserDefaults & Keychain

Application Lifecycle

Auto Layout & Constraints

UITableView & UICollectionView

SwiftUI Basics

SwiftUI State Management

SwiftUI Navigation

Networking & URLSession

Codable & JSON Parsing

Core Data

Protocol Oriented Programming

MVVM Architecture

Push Notifications

Unit Testing & XCTest

UI Testing

Xcode & Build System

Swift Package Manager

Memory Management & ARC

Combine Framework

Concurrency & async/await

iOS Design Patterns

Performance Optimization

Security & Encryption

SwiftUI Advanced

iOS Application Architecture

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