Navigation path management in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to push a new view controller onto the navigation stack.

iOS Swift

navigationController?.[1](UIViewController(), animated: true)

Drag options to blanks, or click blank then click option'

Apresent

BpopViewController

Cdismiss

DpushViewController

Attempts:

3 left

💡 Hint

Common Mistakes

Using popViewController instead of pushViewController

Using present which is for modal presentation

Use pushViewController to add a new screen to the navigation stack.

2fill in blank

medium

Complete the code to pop the current view controller from the navigation stack.

iOS Swift

navigationController?.[1](animated: true)

Drag options to blanks, or click blank then click option'

ApushViewController

BpopViewController

Cpresent

Ddismiss

Attempts:

3 left

💡 Hint

Common Mistakes

Using pushViewController which adds a screen instead of removing

Using dismiss which is for modal views

Use popViewController to remove the current screen and go back.

3fill in blank

hard

Fix the error in the code to set the root view controller of the navigation controller.

iOS Swift

navigationController?.[1] = [UIViewController()]

Drag options to blanks, or click blank then click option'

AvisibleViewController

BtopViewController

CviewControllers

DrootViewController

Attempts:

3 left

💡 Hint

Common Mistakes

Using rootViewController which is not a property of UINavigationController

Using topViewController which is read-only

The viewControllers property sets the stack of view controllers, starting with the root.

4fill in blank

hard

Fill both blanks to pop to the root view controller with animation.

iOS Swift

navigationController?.[1](animated: [2])

Drag options to blanks, or click blank then click option'

ApopToRootViewController

BpopViewController

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using popViewController which only pops one screen

Setting animation to false which disables transition effect

popToRootViewController(animated: true) returns to the first screen with animation.

5fill in blank

hard

Fill all three blanks to replace the current navigation stack with two new view controllers.

iOS Swift

navigationController?.[1] = [[2], [3]]

Drag options to blanks, or click blank then click option'

AviewControllers

BFirstViewController()

CSecondViewController()

DrootViewController

Attempts:

3 left

💡 Hint

Common Mistakes

Using rootViewController which is not a UINavigationController property

Passing class names instead of instances

Setting viewControllers replaces the stack. Provide new view controller instances in an array.

Practice

1. What does the pushViewController(_:animated:) method do in a UINavigationController?

easy

A. It removes the current screen from the navigation stack.

B. It adds a new screen on top of the current navigation stack.

C. It replaces the entire navigation stack with a new screen.

D. It resets the navigation stack to the root screen.

Solution

1. Step 1: Understand pushViewController behavior

   The method adds a new view controller on top of the current stack, showing a new screen.

2. Step 2: Compare with other navigation actions

   Pop removes the top screen, replace resets stack, so push only adds on top.

3. Final Answer:

   It adds a new screen on top of the current navigation stack. -> Option B

4. Quick Check:

   pushViewController = add new screen [OK]

Hint: Push means add a new screen on top [OK]

Common Mistakes:

• Confusing push with pop (removing screen)
• Thinking push replaces the whole stack
• Assuming push resets to root screen

2. Which of the following is the correct Swift syntax to pop the current view controller from a navigation stack?

easy

A. navigationController.popViewController(animated: true)

B. navigationController.pushViewController(animated: true)

C. navigationController.pop(animated: true)

D. navigationController.removeViewController(animated: true)

Solution

1. Step 1: Recall the correct method name

   The method to remove the top view controller is popViewController(animated:).

2. Step 2: Check method usage

   It is called on the navigationController instance with a Bool for animation.

3. Final Answer:

   navigationController.popViewController(animated: true) -> Option A

4. Quick Check:

   Pop method is popViewController(animated:) [OK]

Hint: Pop removes top screen, method ends with ViewController [OK]

Common Mistakes:

• Using push instead of pop
• Using incorrect method names like pop() or removeViewController()
• Missing the animated parameter

3. Consider this Swift code snippet inside a view controller:

navigationController?.pushViewController(detailVC, animated: true)
navigationController?.popViewController(animated: true)
navigationController?.popViewController(animated: true)

If the navigation stack initially has 3 view controllers, how many view controllers remain after this code runs?

medium

A. 2

B. 1

C. 3

D. 0

Solution

1. Step 1: Analyze push action

   Push adds 1 view controller, so stack goes from 3 to 4.

2. Step 2: Analyze two pop actions

   Each pop removes 1 view controller, so 4 - 2 = 2 remain.

3. Step 3: Confirm final count

   After two pops, 2 view controllers remain on the stack.

4. Final Answer:

   2 -> Option A

5. Quick Check:

   3 + 1 - 2 = 2 [OK]

Hint: Push adds 1, each pop removes 1 [OK]

Common Mistakes:

• Forgetting push adds a controller
• Counting only one pop instead of two
• Assuming stack can't go below 3

4. You wrote this code to pop to the root view controller:

navigationController.popToRootViewController(animated: true)

But your app crashes with an error. What is the most likely cause?

medium

A. animated parameter must be false to avoid crashes.

B. popToRootViewController requires a completion handler parameter.

C. navigationController is nil because the view controller is not inside a navigation stack.

D. You must call popViewController instead of popToRootViewController.

Solution

1. Step 1: Understand navigationController optional

   navigationController is optional and can be nil if the current controller is not inside a navigation stack.

2. Step 2: Check method requirements

   popToRootViewController(animated:) does not require a completion handler and accepts true or false for animation.

3. Final Answer:

   navigationController is nil because the view controller is not inside a navigation stack. -> Option C

4. Quick Check:

   Nil navigationController causes crash [OK]

Hint: Check if navigationController is nil before popping [OK]

Common Mistakes:

• Assuming popToRootViewController needs completion handler
• Thinking animated must be false
• Confusing popViewController with popToRootViewController

5. You want to replace the entire navigation stack with a new set of view controllers: [homeVC, profileVC, settingsVC]. Which code snippet correctly achieves this?

hard

A. navigationController.popViewController(animated: true)

B. navigationController.pushViewController(settingsVC, animated: true)

C. navigationController.popToRootViewController(animated: true)

D. navigationController.setViewControllers([homeVC, profileVC, settingsVC], animated: true)

Solution

1. Step 1: Identify method to replace stack

   The method setViewControllers(_:animated:) replaces the entire navigation stack with the given array.

2. Step 2: Compare other options

   Push adds one controller, popToRoot pops to root only, popViewController pops one controller.

3. Final Answer:

   navigationController.setViewControllers([homeVC, profileVC, settingsVC], animated: true) -> Option D

4. Quick Check:

   setViewControllers replaces stack [OK]

Hint: Use setViewControllers to replace whole stack [OK]

Common Mistakes:

• Using push to add instead of replace
• Using pop methods which only remove controllers
• Forgetting to pass array of controllers