Project structure in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the role of Info.plist in an iOS project

What is the primary purpose of the Info.plist file in an iOS Swift project?

A It contains the Swift source code for the app's main view controller.

B It stores configuration data like app permissions and display name used by the system.

C It manages the app's user interface layout and constraints.

D It holds the compiled binary executable of the app.

💡 Hint

Think about what the system needs to know about your app before running it.

Info.plist is a property list file that holds key-value pairs describing app settings like permissions, app name, icon files, and launch screen info. It is not source code or UI layout.

❓ ui_behavior

intermediate

Locating the main storyboard in an iOS project

In a typical iOS Swift project using storyboards, where is the main storyboard file referenced so the app knows which UI to load first?

A In the Info.plist file under the key "UIMainStoryboardFile".

B Inside the AppDelegate.swift file as a string constant.

C In the Assets.xcassets folder as an image set.

D In the LaunchScreen.storyboard file.

💡 Hint

This setting tells the system which storyboard to load at app launch.

The Info.plist file contains the key "UIMainStoryboardFile" which points to the main storyboard file. This tells iOS which UI to load first.

❓ lifecycle

advanced

Order of files executed at app launch

Which sequence correctly describes the order of execution when an iOS Swift app launches?

A 2, 1, 3, 4

B 3, 1, 2, 4

C 1, 2, 3, 4

D 1, 3, 2, 4

💡 Hint

Think about what happens first: system call, app delegate, UI loading, then showing window.

UIApplicationMain is the entry point that sets up the app. Then AppDelegate's launch method runs. After that, the main storyboard loads the UI, and finally the window is shown.

❓ navigation

advanced

Where to add new Swift files for view controllers

In a well-organized iOS Swift project, where should you place new Swift files that define view controllers?

A In the Info.plist file as embedded code.

B Inside the LaunchScreen.storyboard file.

C Directly inside the Assets.xcassets folder.

D Inside a dedicated folder named "ViewControllers" or similar within the project directory.

💡 Hint

Think about keeping code files organized by their role.

Source code files like view controllers should be in dedicated folders for clarity and maintenance. Assets and storyboards are for images and UI layouts, not code.

🔧 Debug

expert

Why does the app crash on launch after renaming the main storyboard file?

You renamed your main storyboard file from "Main.storyboard" to "Start.storyboard" but did not update any other files. What is the most likely cause of the app crashing on launch?

A The Info.plist still references "Main" as the main storyboard file, causing a missing file error.

B The AppDelegate.swift file must be renamed to match the storyboard name.

C The Assets.xcassets folder needs to be updated with the new storyboard name.

D The LaunchScreen.storyboard must be deleted to avoid conflicts.

💡 Hint

Check where the system looks for the initial UI file.

The Info.plist file still points to the old storyboard name "Main". Since the file was renamed to "Start", the app cannot find the storyboard and crashes.

Practice

1. Which file in an iOS Swift project is primarily responsible for handling app launch and life cycle events?

easy

A. ViewController.swift

B. AppDelegate.swift

C. Assets.xcassets

D. Info.plist

Solution

1. Step 1: Understand the role of AppDelegate.swift

   AppDelegate.swift manages app launch, termination, and state transitions.

2. Step 2: Compare with other files

   ViewController.swift manages UI screens, Assets.xcassets holds images, Info.plist stores configuration.

3. Final Answer:

   AppDelegate.swift -> Option B

4. Quick Check:

   App life cycle = AppDelegate.swift [OK]

Hint: AppDelegate handles app start and life cycle events [OK]

Common Mistakes:

• Confusing ViewController with AppDelegate
• Thinking Assets.xcassets manages app life cycle
• Assuming Info.plist handles launch events

2. Which of the following is the correct way to reference an image named "icon" stored in the Assets.xcassets folder in SwiftUI?

easy

A. Image("icon")

B. UIImage(named: "icon")

C. Image.asset("icon")

D. UIImageView("icon")

Solution

1. Step 1: Identify SwiftUI image syntax

   In SwiftUI, images from assets are loaded using Image("imageName").

2. Step 2: Differentiate UIKit and SwiftUI

   UIImage(named:) is UIKit, not SwiftUI; Image.asset and UIImageView("icon") are invalid syntax.

3. Final Answer:

   Image("icon") -> Option A

4. Quick Check:

   SwiftUI image = Image("icon") [OK]

Hint: Use Image("name") for assets in SwiftUI [OK]

Common Mistakes:

• Using UIKit UIImage(named:) in SwiftUI code
• Trying non-existent Image.asset method
• Confusing UIImageView constructor with Image

3. Given this code snippet in an iOS project:

let window = UIWindow(frame: UIScreen.main.bounds)
window.rootViewController = UIViewController()
window.makeKeyAndVisible()

What is the purpose of this code in the project structure?

medium

A. To define app life cycle methods

B. To load images from Assets.xcassets

C. To create and display the main app window with a root view controller

D. To configure app permissions in Info.plist

Solution

1. Step 1: Analyze UIWindow creation

   The code creates a UIWindow sized to the screen and sets its rootViewController.

2. Step 2: Understand makeKeyAndVisible()

   This method makes the window visible and key for user interaction.

3. Final Answer:

   To create and display the main app window with a root view controller -> Option C

4. Quick Check:

   UIWindow setup = display main window [OK]

Hint: UIWindow with rootViewController shows main screen [OK]

Common Mistakes:

• Confusing window setup with image loading
• Thinking this code manages app life cycle
• Assuming it edits Info.plist settings

4. You see this error in your iOS project: "SceneDelegate.swift not found". What is the most likely cause?

medium

A. The project was created without a SceneDelegate file, but the Info.plist expects it

B. Assets.xcassets folder is missing

C. AppDelegate.swift is empty

D. Storyboard file is corrupted

Solution

1. Step 1: Understand SceneDelegate role

   SceneDelegate manages UI scenes in multi-window apps, required if Info.plist references it.

2. Step 2: Identify mismatch

   If SceneDelegate.swift is missing but Info.plist expects it, app will error.

3. Final Answer:

   The project was created without a SceneDelegate file, but the Info.plist expects it -> Option A

4. Quick Check:

   Missing SceneDelegate file = Info.plist mismatch [OK]

Hint: Check Info.plist and project files match for SceneDelegate [OK]

Common Mistakes:

• Blaming missing assets for SceneDelegate error
• Assuming empty AppDelegate causes this error
• Thinking storyboard corruption causes SceneDelegate error

5. You want to organize your iOS project so that all UI layouts are stored separately from code files. Which folder should you use to store these layouts?

hard

A. Models folder

B. Assets.xcassets folder

C. Supporting Files folder

D. Storyboard folder

Solution

1. Step 1: Identify UI layout storage

   Storyboards hold UI layouts visually designed for screens.

2. Step 2: Differentiate other folders

   Assets.xcassets holds images, Supporting Files hold config files, Models hold data structures.

3. Final Answer:

   Storyboard folder -> Option D

4. Quick Check:

   UI layouts = Storyboard folder [OK]

Hint: Store UI layouts in Storyboard folder, not assets or models [OK]

Common Mistakes:

• Putting UI layouts in Assets.xcassets
• Confusing Supporting Files with UI storage
• Storing layouts in Models folder