swift-swiftui

name	swift-swiftui
description	Standards for State Management, View Lifecycle, and Property Wrappers. Use when managing SwiftUI state, view lifecycle, or property wrappers like @State and @Binding. (triggers: **/*.swift, @State, @Binding, @ObservedObject, View, body)

SwiftUI Standards

Priority: P0

Implementation Guidelines

State Management

• @State: @State for data owned by the view (e.g., toggle, text input). Private to the view.
• @Binding: @Binding for data passed down from a parent to a child. Two-way connection.
• @ObservedObject: @ObservedObject when receiving an instance from an external source.
• @StateObject: @StateObject when the view is creating the object instance. View owns lifecycle.
• @EnvironmentObject: inject data into the view's hierarchy via .environmentObject(). Shared across view hierarchy.

View Composition

• Extract Subviews: Keep views small (<200 lines). Extract reusable components.
• View Modifiers: Chain modifiers for styling (.font(), .padding()).
• Custom Modifiers: Create ViewModifier for reusable styles.

Performance

• Avoid Heavy Computation: Use @State + .task() for async work.
• Equatable: Conform views to Equatable to prevent unnecessary re-renders.
• LazyStacks: Use LazyVStack/LazyHStack when displaying a large number of views in a scrolling container to load them only as they appear.

Anti-Patterns

• No @ObservedObject for owned objects: Use @StateObject.
• No logic in body: Move to computed properties or methods.
• No ! in View: Use if-let or nil coalescing.

References

• State & Binding