swift_swiftui

SwiftUI This skill covers SwiftUI framework concepts for building declarative user interfaces. Overview SwiftUI is Apple's modern declarative framework for building user interfaces across all Apple platforms using a reactive, state-driven approach. Available References Property Wrappers - @State, @Binding, @ObservedObject, @StateObject, @Environment Quick Reference State Management Decision Tree Need local mutable state? ├── YES → Is it a value type? │ ├── YES → Use @State │ └── NO → Use @StateObject └── NO → Shared from parent? ├── YES → Is it value type? │ ├── YES → Use @Binding │ └── NO → Use @ObservedObject └── NO → Use @Environment Property Wrappers Wrapper Owns Data Data Type Use For @State Yes Value type Local UI state @Binding No Value type Shared state with parent @ObservedObject No Reference type Injected dependencies @StateObject Yes Reference type Owned view models @Environment No Any Shared resources Common Usage Patterns // Local state struct CounterView : View { @State private var count = 0 var body : some View { Button ( "Count: ( count ) " ) { count += 1 } } } // Shared state (parent to child) struct ParentView : View { @State private var isOn = false var body : some View { ChildView ( isOn : $isOn ) } } struct ChildView : View { @Binding var isOn : Bool var body : some View { Toggle ( "Enable" , isOn : $isOn ) } } // Observable object class ViewModel : ObservableObject { @Published var items : [ Item ] = [ ] } struct ContentView : View { @StateObject private var viewModel = ViewModel ( ) var body : some View { List ( viewModel . items ) { item in Text ( item . name ) } } } // Environment values struct EnvironmentView : View { @Environment ( \ . colorScheme ) var colorScheme @Environment ( \ . dismiss ) var dismiss var body : some View { Text ( colorScheme == . dark ? "Dark" : "Light" ) } } Best Practices Use @State for local UI state - Toggles, text fields, counters Lift state up when shared - Single source of truth Use @StateObject for owned view models - Survives view recreation Pass @Binding to child views - Two-way data flow Keep @State minimal - Only store what's needed for UI Use @Environment for system values - Color scheme, locale, etc. Access on main thread - All property wrappers require @MainActor Initialize with underscore - _count = State(initialValue:) Common Pitfalls Pitfall Solution Initializing @State directly Use _property = State(initialValue:) Creating @ObservedObject in init Use @StateObject instead Mutating on background thread Dispatch to main queue Passing @State instead of Binding Use $property for Binding For More Information Visit https://swiftzilla.dev for comprehensive SwiftUI documentation.