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How to create basic animations

Paul Hudson    @twostraws   

Updated for Xcode 13.0 beta 2

SwiftUI has built-in support for animations with its animation() modifier. To use this modifier, place it after any other modifiers for your views, tell it what kind of animation you want, and also make sure you attach it to a particular value so the animation triggers only when that specific value changes.

For example, this code creates a button that increases its scale effect by 1 each time it’s pressed:

struct ContentView: View {
    @State private var scale: CGFloat = 1

    var body: some View {
        Button("Press here") {
            scale += 1
        }
        .scaleEffect(scale)
        .animation(.linear(duration: 1), value: scale)
    }
}

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That makes the animation happen over 1 second, but if you don’t want to specify a precise time for your animation you can just use .linear.

Instead of simple linear animations, you can specify a curve from .easeIn, .easeOut, .easeInOut, or use .timingCurve to specify your own control points.

For example, this animates the scale effect so that it starts slow and gets faster:

struct ContentView: View {
    @State private var scale: CGFloat = 1

    var body: some View {
        Button("Press here") {
            scale += 1
        }
        .scaleEffect(scale)
        .animation(.easeIn, value: scale)
    }
}

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You can animate many other modifiers, such as 2D and 3D rotation, opacity, border, and more. For example, this makes a button that spins around and increases its border every time it’s tapped:

struct ContentView: View {
    @State private var angle: Double = 0
    @State private var borderThickness: CGFloat = 1

    var body: some View {
        Button("Press here") {
            angle += 45
            borderThickness += 1
        }
        .padding()
        .border(Color.red, width: borderThickness)
        .rotationEffect(.degrees(angle))
        .animation(.easeIn, value: angle)
    }
}

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