swift_swiftui（Swift swiftui 命令行）

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

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

1. Use @State for local UI state - Toggles, text fields, counters
2. Lift state up when shared - Single source of truth
3. Use @StateObject for owned view models - Survives view recreation
4. Pass @Binding to child views - Two-way data flow
5. Keep @State minimal - Only store what's needed for UI
6. Use @Environment for system values - Color scheme, locale, etc.
7. Access on main thread - All property wrappers require @MainActor
8. Initialize with underscore - _count = State(initialValue:)

Common Pitfalls

For More Information

Visit https://swiftzilla.dev for comprehensive SwiftUI documentation.