ax-swiftui

SwiftUI

Quick Patterns

State Management (iOS 17+)

Property Wrapper Decision Tree:

Which wrapper?
|-- View owns the data?        --> @State
|-- App-wide shared model?     --> @Environment
|-- Need bindings to parent?   --> @Bindable
|-- Just reading passed data?  --> Plain property (no wrapper)

@Observable replaces ObservableObject (iOS 17+):

@Observable
class Model {
    var count = 0         // No @Published needed
}

// View automatically tracks accessed properties
struct MyView: View {
    @State private var model = Model()   // Owned
    // OR
    var model: Model                     // Passed in (no wrapper)
    // OR
    @Bindable var model: Model           // Need $model.count bindings
    // OR
    @Environment(Model.self) var model   // From environment
}

Pre-iOS 17 (ObservableObject):

• @StateObject -- view owns the instance
• @ObservedObject -- injected from parent
• @EnvironmentObject -- shared via environment

Navigation (iOS 16+)

NavigationStack with typed path:

@State private var path: [Recipe] = []

NavigationStack(path: $path) {
    List(recipes) { recipe in
        NavigationLink(recipe.name, value: recipe)
    }
    .navigationDestination(for: Recipe.self) { recipe in
        RecipeDetail(recipe: recipe)
    }
}

func popToRoot() { path.removeAll() }

NavigationPath for heterogeneous types + deep linking:

@State private var path = NavigationPath()

NavigationStack(path: $path) {
    HomeView()
        .navigationDestination(for: Category.self) { CategoryView(category: $0) }
        .navigationDestination(for: Recipe.self) { RecipeDetail(recipe: $0) }
}
.onOpenURL { url in handleDeepLink(url) }

func handleDeepLink(_ url: URL) {
    path.removeLast(path.count)  // Pop to root first
    // Parse URL, append values in parent-to-child order
}

TabView with per-tab stacks (iOS 18+):

TabView {
    Tab("Home", systemImage: "house") {
        NavigationStack { HomeView() }
    }
    Tab("Search", systemImage: "magnifyingglass") {
        NavigationStack { SearchView() }
    }
}