swiftui-view-refactor – skill Lập trình cho agent AI

SwiftUI View Refactor

Overview

Refactor SwiftUI views toward small, explicit, stable view types. Default to vanilla SwiftUI: local state in the view, shared dependencies in the environment, business logic in services/models, and view models only when the request or existing code clearly requires one.

When to Use

• When cleaning up a large SwiftUI view or splitting long body implementations.
• When you need smaller subviews, explicit dependency injection, or better Observation usage.

Core Guidelines

1) View ordering (top → bottom)

• Enforce this ordering unless the existing file has a stronger local convention you must preserve.
• Environment
• private/public let
• @State / other stored properties
• computed var (non-view)
• init
• body
• computed view builders / other view helpers
• helper / async functions

2) Default to MV, not MVVM

• Views should be lightweight state expressions and orchestration points, not containers for business logic.
• Favor @State, @Environment, @Query, .task, .task(id:), and onChange before reaching for a view model.
• Inject services and shared models via @Environment; keep domain logic in services/models, not in the view body.
• Do not introduce a view model just to mirror local view state or wrap environment dependencies.
• If a screen is getting large, split the UI into subviews before inventing a new view model layer.

3) Strongly prefer dedicated subview types over computed some View helpers

• Flag body properties that are longer than roughly one screen or contain multiple logical sections.
• Prefer extracting dedicated View types for non-trivial sections, especially when they have state, async work, branching, or deserve their own preview.
• Keep computed some View helpers rare and small. Do not build an entire screen out of private var header: some View-style fragments.
• Pass small, explicit inputs (data, bindings, callbacks) into extracted subviews instead of handing down the entire parent state.
• If an extracted subview becomes reusable or independently meaningful, move it to its own file.

Prefer:

var body: some View {
    List {
        HeaderSection(title: title, subtitle: subtitle)
        FilterSection(
            filterOptions: filterOptions,
            selectedFilter: $selectedFilter
        )
        ResultsSection(items: filteredItems)
        FooterSection()
    }
}

private struct HeaderSection: View {
    let title: String
    let subtitle: String

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

private struct FilterSection: View {
    let filterOptions: [FilterOption]
    @Binding var selectedFilter: FilterOption

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

Avoid:

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)
    }
}

3b) Extract actions and side effects out of body

• Do not keep non-trivial button actions inline in the view body.
• Do not bury business logic inside .task, .onAppear, .onChange, or .refreshable.
• Prefer calling small private methods from the view, and move real business logic into services/models.
• The body should read like UI, not like a view controller.

Button("Save", action: save)
    .disabled(isSaving)

.task(id: searchText) {
    await reload(for: searchText)
}

private func save() {
    Task { await saveAsync() }
}

private func reload(for searchText: String) async {
    guard !searchText.isEmpty else {
        results = []
        return
    }
    await searchService.search(searchText)
}

4) Keep a stable view tree (avoid top-level conditional view swapping)

• Avoid body or computed views that return completely different root branches via if/else.
• Prefer a single stable base view with conditions inside sections/modifiers (overlay, opacity, disabled, toolbar, etc.).
• Root-level branch swapping causes identity churn, broader invalidation, and extra recomputation.

Prefer:

var body: some View {
    List {
        documentsListContent
    }
    .toolbar {
        if canEdit {
            editToolbar
        }
    }
}

Avoid:

var documentsListView: some View {
    if canEdit {
        editableDocumentsList
    } else {
        readOnlyDocumentsList
    }
}

5) View model handling (only if already present or explicitly requested)

• Treat view models as a legacy or explicit-need pattern, not the default.
• 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 create the view model in the view's init.
• Avoid bootstrapIfNeeded patterns and other delayed setup workarounds.

Example (Observation-based):

@State private var viewModel: SomeViewModel

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

6) Observation usage

• For @Observable reference types on iOS 17+, store them as @State in the owning view.
• Pass observables down explicitly; avoid optional state unless the UI genuinely needs it.
• If the deployment target includes iOS 16 or earlier, use @StateObject at the owner and @ObservedObject when injecting legacy observable models.

Workflow

1. Reorder the view to match the ordering rules.

2. Remove inline actions and side effects from body; move business logic into services/models and keep only thin orchestration in the view.

3. Shorten long bodies by extracting dedicated subview types; avoid rebuilding the screen out of many computed some View helpers.

4. Ensure stable view structure: avoid top-level if-based branch swapping; move conditions to localized sections/modifiers.

5. If a view model exists or is explicitly required, preserve its ownership and lifetime: use @State for owned @Observable models, or @StateObject/@ObservedObject for legacy ObservableObject; do not mechanically change wrappers.

6. Confirm Observation usage: @State for root @Observable models on iOS 17+, legacy wrappers only when the deployment target requires them.

7. Keep behavior intact: do not change layout or business logic unless requested.

Notes

• Prefer small, explicit view types over large conditional blocks and large computed some View properties.
• Keep computed view builders below body and non-view computed vars above init.
• A good SwiftUI refactor should make the view read top-to-bottom as data flow plus layout, not as mixed layout and imperative logic.
• For MV-first guidance and rationale, see references/mv-patterns.md.

Large-view handling

When a SwiftUI view file exceeds ~300 lines, split it aggressively. Extract meaningful sections into dedicated View types instead of hiding complexity in many computed properties. Use private extensions with // MARK: - comments for actions and helpers, but do not treat extensions as a substitute for breaking a giant screen into smaller view types. If an extracted subview is reused or independently meaningful, move it into its own file.

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.