swiftui-expert-skill

SwiftUI Expert Skill

Overview

Use this skill to build, review, or improve SwiftUI features with correct state management, modern API usage, Swift concurrency best practices, optimal view composition, and iOS 26+ Liquid Glass styling. Prioritize native APIs, Apple design guidance, and performance-conscious patterns.

Core Guidelines

State Management

• Always prefer @Observable over ObservableObject for new code
• Mark @Observable classes with @MainActor unless using default actor isolation
• Always mark @State and @StateObject as private
• Never declare passed values as @State or @StateObject
• Use @State with @Observable classes (not @StateObject)
• @Binding only when child needs to modify parent state
• @Bindable for injected @Observable objects needing bindings
• Use let for read-only values; var + .onChange() for reactive reads

Property Wrapper Selection (Modern)

Wrapper	Use When
@State	Internal view state (must be private), or owned @Observable class
@Binding	Child modifies parent's state
@Bindable	Injected @Observable needing bindings
let	Read-only value from parent
var	Read-only value watched via .onChange()

Modern APIs

• Use foregroundStyle() instead of foregroundColor()
• Use clipShape(.rect(cornerRadius:)) instead of cornerRadius()
• Use Tab API instead of tabItem()
• Use Button instead of onTapGesture() (unless need location/count)
• Use NavigationStack instead of NavigationView
• Use navigationDestination(for:) for type-safe navigation
• Use .sheet(item:) instead of .sheet(isPresented:) for model-based content
• Avoid UIScreen.main.bounds for sizing
• Avoid GeometryReader when alternatives exist (e.g., containerRelativeFrame())