Transition effects in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the visible effect of this transition code?

Consider this Swift code snippet for a view controller transition. What visual effect will the user see when this transition runs?

iOS Swift

let transition = CATransition()
transition.duration = 0.5
transition.type = CATransitionType.push
transition.subtype = CATransitionSubtype.fromRight
view.window?.layer.add(transition, forKey: nil)
navigationController?.popViewController(animated: false)

A The new screen slides in from the right side over the current screen.

B The new screen fades in over the current screen.

C The new screen slides in from the left side over the current screen.

D The new screen zooms in from the center.

💡 Hint

Look at the transition type and subtype properties to understand the direction and style.

The CATransition with type 'push' and subtype 'fromRight' causes the new view to slide in from the right side, pushing the old view out.

❓ lifecycle

intermediate

When does the transition animation start in this code?

Given this code snippet inside a UIViewController, at what point does the transition animation begin?

iOS Swift

override func viewWillDisappear(_ animated: Bool) {
  super.viewWillDisappear(animated)
  let transition = CATransition()
  transition.duration = 0.3
  transition.type = CATransitionType.fade
  view.window?.layer.add(transition, forKey: nil)
}

A Right after the view has disappeared from the screen.

B Right before the view disappears from the screen.

C When the view appears on the screen.

D When the view is loaded into memory.

💡 Hint

Check which lifecycle method is overridden and when it is called.

The viewWillDisappear method is called just before the view disappears, so the transition animation starts then.

📝 Syntax

advanced

What error does this transition code produce?

Analyze this Swift code snippet for a transition. What error will it cause when compiled?

iOS Swift

let transition = CATransition()
transition.duration = 0.4
transition.type = "slide"
view.window?.layer.add(transition, forKey: nil)

A Syntax error: Missing parentheses in method call.

B Runtime error: Unknown transition type causes crash.

C No error, code runs and shows slide transition.

D Type error: Cannot assign String to CATransitionType.

💡 Hint

Check the type of the 'type' property and what values it accepts.

There is a compile-time error because the 'type' property expects a CATransitionType, not a String. "slide" is not a valid CATransitionType.

❓ navigation

advanced

Which option correctly adds a custom transition when pushing a new view controller?

You want to push a new view controller with a fade transition. Which code snippet correctly achieves this?

A

let transition = CATransition()
transition.duration = 0.5
transition.type = CATransitionType.fade
view.layer.add(transition, forKey: nil)
navigationController?.pushViewController(newVC, animated: false)

B

let transition = CATransition()
transition.duration = 0.5
transition.type = CATransitionType.fade
navigationController?.pushViewController(newVC, animated: true)
navigationController?.view.layer.add(transition, forKey: nil)

C

let transition = CATransition()
transition.duration = 0.5
transition.type = CATransitionType.fade
navigationController?.view.layer.add(transition, forKey: nil)
navigationController?.pushViewController(newVC, animated: false)

D

let transition = CATransition()
transition.duration = 0.5
transition.type = CATransitionType.fade
newVC.view.layer.add(transition, forKey: nil)
navigationController?.pushViewController(newVC, animated: false)

💡 Hint

The transition must be added to the navigation controller's view layer before pushing without animation.

Adding the transition to navigationController?.view.layer before pushing with animated: false triggers the custom animation correctly.

🧠 Conceptual

expert

Why might a custom CATransition not appear when pushing a view controller?

You added a CATransition to the window's layer before pushing a view controller, but the animation does not show. What is the most likely reason?

A The pushViewController call uses animated: true, which overrides the custom transition.

B The window's layer cannot display animations.

C The CATransition type is not set, so no animation occurs.

D The new view controller's view is nil at the time of transition.

💡 Hint

Check the animated parameter in the navigation call.

If animated: true is used, the default navigation animation overrides the custom CATransition animation.