/performance

Performance

• When toggling modifier values, prefer ternary expressions over if/else view branching to avoid _ConditionalContent, preserve structural identity, and avoid repeatedly recreating underlying platform views.
• Avoid AnyView unless absolutely required. Use @ViewBuilder, Group, or generics instead.
• If a ScrollView has an opaque, static, and solid background, prefer to use scrollContentBackground(.visible) to improve scroll-edge rendering efficiency.
• It is more efficient to break views up by making dedicated SwiftUI views rather than place them into computed properties or methods. Using @ViewBuilder on a property or method does not solve this; breaking views up is strongly preferred.
• Always ensure view initializers are kept as small and simple as possible, avoiding any non-trivial work. Flag any work that can be moved into a task() modifier to be run when the view is shown.
• Similarly, assume each view’s body property is called frequently – if logic such as sorting or filtering can be moved out of there easily, it should be.
• Avoid creating properties to store formatters such as DateFormatter unless they are required. A more natural approach is to use Text with a format, like this: Text(Date.now, format: .dateTime.day().month().year()) or Text(100, format: .currency(code: "USD")).
• Avoid expensive inline transforms in List/ForEach initializers (e.g. items.filter { ... }) when they are repeated often.
• Prefer deriving transformed data from the source-of-truth using let, or caching in @State. However, do not cache derived collections in @State unless you also own explicit invalidation logic to avoid stale UI.
• For large data sets in ScrollView, use LazyVStack/LazyHStack; flag eager stacks with many children.
• Prefer using task() over onAppear() when doing async work, because it will be cancelled automatically when the view disappears.
• Avoid storing escaping @ViewBuilder closures on views when possible; store built view results instead.

Example:

// Anti-pattern: stores an escaping closure on the view.
struct CardView<Content: View>: View {
    let content: () -> Content

    var body: some View {
        VStack(alignment: .leading) {
            content()
        }
        .padding()
        .background(.ultraThinMaterial)
        .clipShape(.rect(cornerRadius: 8))
    }
}

// Preferred: store the built view value; the synthesized init handles calling the builder.
struct CardView<Content: View>: View {
    @ViewBuilder let content: Content

    var body: some View {
        VStack(alignment: .leading) {
            content
        }
        .padding()
        .background(.ultraThinMaterial)
        .clipShape(.rect(cornerRadius: 8))
    }
}