swiftui-view-refactor（Swiftui 视图重构）

SwiftUI View Refactor

Overview

Apply a consistent structure and dependency pattern to SwiftUI views, with a focus on ordering, Model-View (MV) patterns, careful view model handling, and correct Observation usage.

Core Guidelines

1) View ordering (top → bottom)

• Environment
• private/public let
• @State / other stored properties
• computed var (non-view)
• init
• body
• computed view builders / other view helpers
• helper / async functions

2) Prefer MV (Model-View) patterns

• Default to MV: Views are lightweight state expressions; models/services own business logic.
• Favor @State, @Environment, @Query, and task/onChange for orchestration.
• Inject services and shared models via @Environment; keep views small and composable.
• Split large views into subviews rather than introducing a view model.

3) Split large bodies and view properties

• If body grows beyond a screen or has multiple logical sections, split it into smaller subviews.
• Extract large computed view properties (var header: some View {...}) into dedicated View types when they carry state or complex branching.
• It's fine to keep related subviews as computed view properties in the same file; extract to a standalone View struct only when it structurally makes sense or when reuse is intended.
• Prefer passing small inputs (data, bindings, callbacks) over reusing the entire parent view state.

Example (extracting a section):

var body: some View {
    VStack(alignment: .leading, spacing: 16) {
        HeaderSection(title: title, isPinned: isPinned)
        DetailsSection(details: details)
        ActionsSection(onSave: onSave, onCancel: onCancel)
    }
}

Example (long body → shorter body + computed views in the same file):

var body: some View {
    List {
        header
        filters
        results
        footer
    }
}

private var header: some View {
    VStack(alignment: .leading, spacing: 6) {
        Text(title).font(.title2)
        Text(subtitle).font(.subheadline)
    }
}

private var filters: some View {
    ScrollView(.horizontal, showsIndicators: false) {
        HStack {
            ForEach(filterOptions, id: \.self) { option in
                FilterChip(option: option, isSelected: option == selectedFilter)
                    .onTapGesture { selectedFilter = option }
            }
        }
    }
}

Example (extracting a complex computed view):

private var header: some View {
    HeaderSection(title: title, subtitle: subtitle, status: status)
}

private struct HeaderSection: View {
    let title: String
    let subtitle: String?
    let status: Status

    var body: some View {
        VStack(alignment: .leading, spacing: 4) {
            Text(title).font(.headline)
            if let subtitle { Text(subtitle).font(.subheadline) }
            StatusBadge(status: status)
        }
    }
}

4) View model handling (only if already present)

• Do not introduce a view model unless the request or existing code clearly calls for one.
• If a view model exists, make it non-optional when possible.
• Pass dependencies to the view via init, then pass them into the view model in the view's init.
• Avoid bootstrapIfNeeded patterns.

Example (Observation-based):

@State private var viewModel: SomeViewModel

init(dependency: Dependency) {
    _viewModel = State(initialValue: SomeViewModel(dependency: dependency))
}

5) Observation usage

• For @Observable reference types, store them as @State in the root view.
• Pass observables down explicitly as needed; avoid optional state unless required.

Workflow

1. Reorder the view to match the ordering rules.
2. Favor MV: move lightweight orchestration into the view using @State, @Environment, @Query, task, and onChange.
3. If a view model exists, replace optional view models with a non-optional @State view model initialized in init by passing dependencies from the view.
4. Confirm Observation usage: @State for root @Observable view models, no redundant wrappers.
5. Keep behavior intact: do not change layout or business logic unless requested.

Notes

• Prefer small, explicit helpers over large conditional blocks.
• Keep computed view builders below body and non-view computed vars above init.
• For MV-first guidance and rationale, see references/mv-patterns.md.

Large-view handling

• When a SwiftUI view file exceeds ~300 lines, split it using extensions to group related helpers. Move async functions and helper functions into dedicated private extensions, separated with // MARK: - comments that describe their purpose (e.g., // MARK: - Actions, // MARK: - Subviews, // MARK: - Helpers). Keep the main struct focused on stored properties, init, and body, with view-building computed vars also grouped via marks when the file is long.