oguzhanvarsak

Interview Questions for iOS Developers

1. Classes vs structs

In Swift, structs are value types whereas classes are reference types. When you copy a struct, you end up with two unique copies of the data. When you copy a class, you end up with two references to one instance of the data. It’s a crucial difference, and it affects your choice between classes or structs. (+ Class extendable, struct does not.)

2. What’s the difference between var and let? Which one would you choose for properties in a struct and why?

Both let and var are for creating variables in Swift. let helps you create immutable variables (constants) while on the other hand var creates mutable variables.

3. What does the mutating keyword mean?

The mutating keyword lets callers know that the method is going to make the value change.

hamdan

 private let disposeBag = DisposeBag()
 
  let selectedButton = Observable.from(
            filterButtons.map { button in
                button.rx.tap.map { button }
            }
        ).merge()

        filterButtons.forEach { button in
            selectedButton.map { $0 == button }

iamchiwon

import AuthenticationServices
import RxCocoa
import RxSwift
import UIKit

@available(iOS 13.0, *)
extension ASAuthorizationController: HasDelegate {
    public typealias Delegate = ASAuthorizationControllerDelegate
}

zfael

/**
 * Usage
 * - npm install loadtest
 * - npx ts-node load-test.ts
 */

import loadtest from 'loadtest';

const method = 'GET';

mspvirajpatel

import Foundation
import AuthenticationServices

@available(iOS 13.0, *)
open class AppleSignInManager: NSObject {
    
    static let shared: AppleSignInManager = AppleSignInManager()
    
    var userData: LoginUserData? = nil
    var isShareImageVideo: Bool = false

hamdan

// 1. First of all, you need to make sure “Device Orientation” only on ‘Portrait’ mode.

//2. Add these two functions to AppDelegate, which helps you deal with embed in nav bar/tab bar situation mentioned above:

protocol Rotatable: AnyObject {
  func resetToPortrait()
}

extension Rotatable where Self: UIViewController {
  func resetToPortrait() {

markusfassbender

import UIKit

class GridStackView<T>: UIStackView where T: UIView {
    
    // MARK: Properties
    
    var numberOfColumns: Int = 2
    
    var items: [T] {
        arrangedSubviews.flatMap { view -> [T] in

iamchiwon

import RxSwift

extension ObservableType {
    public func mapObject<T: Codable>(type: T.Type) -> Observable<T> {
        return flatMap { (data) -> Observable<T> in
            if let data = (data as? (HTTPURLResponse, Data))?.1 {
                return try self.mapObject(type: type, data: data)
            } else if let json = (data as? (HTTPURLResponse, Any))?.1 {
                return try self.mapObjectJSON(type: type, json: json)
            } else {

kimtaesu

enum TestError: Error {
    case test
}


extension ObservableType {
    func retryWhen(
        predicate: @escaping (Error) -> Bool,
        maxRetry: Int,

carson-katri

extension String {
    func foregroundColor(_ color: UIColor) -> NSAttributedString {
        NSAttributedString(string: self, attributes: [.foregroundColor : color])
    }
    func background(_ color: UIColor) -> NSAttributedString {
        NSAttributedString(string: self, attributes: [.backgroundColor: color])
    }
    func underline(_ color: UIColor, style: NSUnderlineStyle = .single) -> NSAttributedString {
        NSAttributedString(string: self, attributes: [.underlineColor: color, .underlineStyle: style.rawValue])
    }