You want to animate a view's opacity from 0 to 1 over 2 seconds when a button is tapped. Which code correctly uses withAnimation to achieve this?

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iOS Swift - Animations

You want to animate a view's opacity from 0 to 1 over 2 seconds when a button is tapped. Which code correctly uses withAnimation to achieve this?

AwithAnimation(.easeOut) { self.opacity = 1; DispatchQueue.main.asyncAfter(deadline: .now() + 2) {} }

BwithAnimation(.linear(duration: 2)) { self.isVisible = true }

CwithAnimation { self.isVisible = true; sleep(2) }

DwithAnimation(.spring()) { self.opacity = 0 }

Step-by-Step Solution

Solution:

Step 1: Identify the animation type and duration
To animate opacity over 2 seconds linearly, use .linear(duration: 2).
Step 2: Check the state change inside withAnimation
Setting isVisible = true triggers the opacity change if bound correctly.
Step 3: Evaluate other options
withAnimation { self.isVisible = true; sleep(2) } uses sleep which blocks UI; withAnimation(.easeOut) { self.opacity = 1; DispatchQueue.main.asyncAfter(deadline: .now() + 2) {} } misuses asyncAfter; withAnimation(.spring()) { self.opacity = 0 } animates opacity to 0, not 1.
Final Answer:
withAnimation(.linear(duration: 2)) { self.isVisible = true } -> Option B
Quick Check:
Use withAnimation with linear duration and state change [OK]

Quick Trick: Use withAnimation with duration and change state inside braces [OK]

Common Mistakes:

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