Spring animations in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the visible effect of this spring animation code?

Consider this Swift code snippet for a UIView animation using spring damping. What will the user see when this code runs?

iOS Swift

UIView.animate(withDuration: 1.0, delay: 0, usingSpringWithDamping: 0.3, initialSpringVelocity: 0.5, options: [], animations: {
  view.frame.origin.y += 100
}, completion: nil)

A The view moves down with a slight bounce and settles quickly.

B The view moves down quickly and bounces several times before settling.

C The view moves down instantly without animation.

D The view moves down smoothly and slowly without bouncing.

💡 Hint

Lower damping values cause more bounce in spring animations.

A low damping value like 0.3 causes the animation to overshoot and bounce multiple times before settling. The initial velocity affects how fast it starts moving.

📝 Syntax

intermediate

Which option correctly uses spring animation with completion handler?

Select the Swift code snippet that correctly performs a spring animation on a view's alpha property and runs a completion block after animation.

A

UIView.animate(duration: 0.5, delay: 0, damping: 0.7, velocity: 1, options: [], animations: {
  view.alpha = 0
}, completion: { finished in
  print("Done")
})

B

UIView.animate(withDuration: 0.5, animations: {
  view.alpha = 0
}, completion: {
  print("Done")
})

C

UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.7, initialSpringVelocity: 1, options: [], animations: {
  view.alpha = 0
}, completion: { finished in
  print("Done")
})

D

UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.7, initialSpringVelocity: 1, animations: {
  view.alpha = 0
})

💡 Hint

Check the method signature for spring animations with completion.

Option C uses the correct method signature including delay, damping, velocity, options, animations, and completion handler.

❓ lifecycle

advanced

What happens if you start a spring animation on a view that is not yet in the view hierarchy?

You create a UIView and start a spring animation on it before adding it to the visible view hierarchy. What is the expected behavior?

A The animation runs but is invisible until the view is added, then it jumps to the final state.

B The app crashes due to invalid animation on a non-visible view.

C The animation runs normally and the view animates when added later.

D The animation does not run and the view appears instantly at the final state when added.

💡 Hint

Animations require the view to be in the window to be visible.

Animations on views not in the hierarchy do not run. When the view is added, it appears immediately at the final state without animation.

❓ navigation

advanced

How to chain two spring animations so the second starts after the first completes?

You want to animate a view moving right with a spring animation, then after it finishes, animate it moving down with another spring animation. Which code snippet achieves this chaining correctly?

A

UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0, options: [], animations: {
  view.frame.origin.x += 100
}, completion: { _ in
  UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0, options: [], animations: {
    view.frame.origin.y += 100
  }, completion: nil)
})

B

UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0, options: [], animations: {
  view.frame.origin.x += 100
})
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0, options: [], animations: {
  view.frame.origin.y += 100
})

C

UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0, options: [], animations: {
  view.frame.origin.x += 100
}, completion: nil)
UIView.animate(withDuration: 0.5, delay: 0.5, usingSpringWithDamping: 0.8, initialSpringVelocity: 0, options: [], animations: {
  view.frame.origin.y += 100
}, completion: nil)

D

UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0, options: [], animations: {
  view.frame.origin.x += 100
}, completion: { _ in
  UIView.animate(withDuration: 0.5, delay: 0.5, usingSpringWithDamping: 0.8, initialSpringVelocity: 0, options: [], animations: {
    view.frame.origin.y += 100
  }, completion: nil)
})

💡 Hint

Use the completion block of the first animation to start the second.

Option A correctly starts the second animation inside the completion block of the first, ensuring sequential execution without extra delay.

🔧 Debug

expert

Why does this spring animation not bounce as expected?

This code is intended to animate a view with a spring effect that bounces, but it moves smoothly without bounce. What is the cause?

iOS Swift

UIView.animate(withDuration: 1.0, delay: 0, usingSpringWithDamping: 1.0, initialSpringVelocity: 0, options: [], animations: {
  view.transform = CGAffineTransform(scaleX: 1.5, y: 1.5)
}, completion: nil)

A The damping value is too high, preventing any bounce effect.

B The initialSpringVelocity is zero, so no bounce occurs.

C The animation duration is too long for bounce to be visible.

D The transform property cannot be animated with spring effects.

💡 Hint

Damping controls how much the animation oscillates.

A damping value of 1.0 means no oscillation; the animation smoothly reaches the final state without bouncing.