100 Days of SwiftUI

Day 33

2026-05-21

Project 6, part 2

More advanced animations (such as gestures and transitions)

Controlling the animation stack

• remember that modifier order on a View matters
• remember also that an animation() modifier will implicity animate changes to the view
• .animation() will affect every view above it
  • up to the previous animation
• therefore you can stack animations within the modifier stack to get complex animations
• you can pass nil to the animation modifier, e.g. .animation(nil, value: someValue)
  • probably a good way to change your mind about whether or not it should be animated

Animating gestures

• taps, drags, etc
• CGSize is from Apple framework Core Graphics
• Swift has the offset() modifier to allow us to move a view around without moving other views around it
  • it can take a CGSize
• gesture() modifier goes on the view that’s going to move
  • DragGesture() has 2 closures, for example:

.gesture(
    DragGesture()
        .onChanged { dragAmount = $0.translation }
        .onEnded { _ in dragAmount = .zero }
)

// relies on this: @State private var dragAmount = CGSize.zero

Oh yeah you can make fun (and really annoying) stuff happen!

Showing and hiding views with transitions

• works with conditionals to make view changes look nice
• .transition() modifier
  • can be asymmetric: .transition(.asymmetric(insertion: .scale, removal: .opacity))

Building custom transitions using ViewModifier

• pretty straightforward to make your own transitions
• say, for example, you want to fix an anchor point for a rotation
  • use a UnitPoint
• create a ViewModifier, then extend AnyTransition to create the easier-to-use modifier

I’m reminded of this everlasting line: