fosmvvm-swiftui-view-generator（fosmvvm swiftui 视图生成器）

FOSMVVM SwiftUI View Generator

Generate SwiftUI views that render FOSMVVM ViewModels.

Conceptual Foundation

For full architecture context, see FOSMVVMArchitecture.md | OpenClaw reference

In FOSMVVM, Views are thin rendering layers that display ViewModels:

┌─────────────────────────────────────────────────────────────┐
│                    ViewModelView Pattern                     │
├─────────────────────────────────────────────────────────────┤
│                                                              │
│  ViewModel (Data)          ViewModelView (SwiftUI)          │
│  ┌──────────────────┐     ┌──────────────────┐             │
│  │ title: String    │────►│ Text(vm.title)   │             │
│  │ items: [Item]    │────►│ ForEach(vm.items)│             │
│  │ isEnabled: Bool  │────►│ .disabled(!...)  │             │
│  └──────────────────┘     └──────────────────┘             │
│                                                              │
│  Operations (Actions)                                        │
│  ┌──────────────────┐     ┌──────────────────┐             │
│  │ submit()         │◄────│ Button(action:)  │             │
│  │ cancel()         │◄────│ .onAppear { }    │             │
│  └──────────────────┘     └──────────────────┘             │
│                                                              │
└─────────────────────────────────────────────────────────────┘

Key principle: Views don't transform or compute data. They render what the ViewModel provides.

View-ViewModel Alignment

The View filename should match the ViewModel it renders.

Sources/
  {ViewModelsTarget}/
    {Feature}/
      {Feature}ViewModel.swift        ←──┐
      {Entity}CardViewModel.swift     ←──┼── Same names
                                          │
  {ViewsTarget}/                          │
    {Feature}/                            │
      {Feature}View.swift             ────┤  (renders {Feature}ViewModel)
      {Entity}CardView.swift          ────┘  (renders {Entity}CardViewModel)

This alignment provides:

• Discoverability - Find the view for any ViewModel instantly
• Consistency - Same naming discipline across the codebase
• Maintainability - Changes to ViewModel are reflected in view location

Core Components

1. ViewModelView Protocol

Every view conforms to ViewModelView:

public struct MyView: ViewModelView {
    private let viewModel: MyViewModel

    public var body: some View {
        Text(viewModel.title)
    }

    public init(viewModel: MyViewModel) {
        self.viewModel = viewModel
    }
}

Required:

• private let viewModel: {ViewModel}
• public init(viewModel:)
• Conforms to ViewModelView protocol

2. Operations (Optional)

Interactive views have operations:

public struct MyView: ViewModelView {
    private let viewModel: MyViewModel
    private let operations: MyViewModelOperations

    #if DEBUG
    @State private var repaintToggle = false
    #endif

    public var body: some View {
        Button(action: performAction) {
            Text(viewModel.buttonLabel)
        }
        #if DEBUG
        .testDataTransporter(viewModelOps: operations, repaintToggle: $repaintToggle)
        #endif
    }

    public init(viewModel: MyViewModel) {
        self.viewModel = viewModel
        self.operations = viewModel.operations
    }

    private func performAction() {
        operations.performAction()
        toggleRepaint()
    }

    private func toggleRepaint() {
        #if DEBUG
        repaintToggle.toggle()
        #endif
    }
}

When views have operations:

• Store operations from viewModel.operations in init
• Add @State private var repaintToggle = false (DEBUG only)
• Add .testDataTransporter(viewModelOps:repaintToggle:) modifier (DEBUG only)
• Call toggleRepaint() after every operation invocation

3. Child View Binding

Parent views bind child views using .bind(appState:):

public struct ParentView: ViewModelView {
    @Environment(AppState.self) private var appState
    private let viewModel: ParentViewModel

    public var body: some View {
        VStack {
            Text(viewModel.title)

            // Bind child view with subset of parent's data
            ChildView.bind(
                appState: .init(
                    itemId: viewModel.selectedId,
                    isConnected: viewModel.isConnected
                )
            )
        }
    }
}

The .bind() pattern:

• Child views use .bind(appState:) to receive data from parent
• Parent creates child's AppState from its own ViewModel data
• Enables composition without tight coupling

4. Form Views with Validation

Forms use FormFieldView and Validations environment:

public struct MyFormView: ViewModelView {
    @Environment(Validations.self) private var validations
    @Environment(\.focusState) private var focusField
    @State private var error: Error?

    private let viewModel: MyFormViewModel
    private let operations: MyFormViewModelOperations

    public var body: some View {
        Form {
            FormFieldView(
                fieldModel: viewModel.$email,
                focusField: focusField,
                fieldValidator: viewModel.validateEmail,
                validations: validations
            )

            Button(errorBinding: $error, asyncAction: submit) {
                Text(viewModel.submitButtonLabel)
            }
            .disabled(validations.hasError)
        }
        .onAsyncSubmit {
            await submit()
        }
        .alert(
            errorBinding: $error,
            title: viewModel.errorTitle,
            message: viewModel.errorMessage,
            dismissButtonLabel: viewModel.dismissButtonLabel
        )
    }
}

Form patterns:

• @Environment(Validations.self) for validation state
• FormFieldView for each input field
• Button(errorBinding:asyncAction:) for async actions
• .disabled(validations.hasError) on submit button
• Separate handling for validation errors vs general errors

5. Previews

Use .previewHost() for SwiftUI previews:

#if DEBUG
#Preview {
    MyView.previewHost(
        bundle: MyAppResourceAccess.localizationBundle
    )
    .environment(AppState())
}

#Preview("With Data") {
    MyView.previewHost(
        bundle: MyAppResourceAccess.localizationBundle,
        viewModel: .stub(title: "Preview Title")
    )
    .environment(AppState())
}
#endif

View Categories

Display-Only Views

Views that just render data (no user interactions):

public struct InfoView: ViewModelView {
    private let viewModel: InfoViewModel

    public var body: some View {
        VStack {
            Text(viewModel.title)
            Text(viewModel.description)

            if viewModel.isActive {
                Text(viewModel.activeStatusLabel)
            }
        }
    }

    public init(viewModel: InfoViewModel) {
        self.viewModel = viewModel
    }
}

Characteristics:

• No operations property
• No repaintToggle or testDataTransporter
• Just renders ViewModel properties
• May have conditional rendering based on ViewModel state

Interactive Views

Views with user actions:

public struct ActionView: ViewModelView {
    @State private var error: Error?

    private let viewModel: ActionViewModel
    private let operations: ActionViewModelOperations

    #if DEBUG
    @State private var repaintToggle = false
    #endif

    public var body: some View {
        VStack {
            Button(action: performAction) {
                Text(viewModel.actionLabel)
            }

            Button(role: .cancel, action: cancel) {
                Text(viewModel.cancelLabel)
            }
        }
        .alert(
            errorBinding: $error,
            title: viewModel.errorTitle,
            message: viewModel.errorMessage,
            dismissButtonLabel: viewModel.dismissButtonLabel
        )
        #if DEBUG
        .testDataTransporter(viewModelOps: operations, repaintToggle: $repaintToggle)
        #endif
    }

    public init(viewModel: ActionViewModel) {
        self.viewModel = viewModel
        self.operations = viewModel.operations
    }

    private func performAction() {
        operations.performAction()
        toggleRepaint()
    }

    private func cancel() {
        operations.cancel()
        toggleRepaint()
    }

    private func toggleRepaint() {
        #if DEBUG
        repaintToggle.toggle()
        #endif
    }
}

Form Views

Views with validated input fields:

• Use FormFieldView for each input
• @Environment(Validations.self) for validation state
• Button disabled when validations.hasError
• Separate error handling for validation vs operation errors

Container Views

Views that compose child views:

public struct ContainerView: ViewModelView {
    @Environment(AppState.self) private var appState
    private let viewModel: ContainerViewModel
    private let operations: ContainerViewModelOperations

    public var body: some View {
        VStack {
            switch viewModel.state {
            case .loading:
                ProgressView()

            case .ready:
                ChildAView.bind(
                    appState: .init(id: viewModel.selectedId)
                )

                ChildBView.bind(
                    appState: .init(
                        isActive: viewModel.isActive,
                        level: viewModel.level
                    )
                )
            }
        }
    }
}

When to Use This Skill

• Creating a new SwiftUI view for a FOSMVVM app
• Building UI to render a ViewModel
• Following an implementation plan that requires new views
• Creating forms with validation
• Building container views that compose child views

What This Skill Generates

Note: The corresponding ViewModel and ViewModelOperations should already exist (use fosmvvm-viewmodel-generator skill).

Project Structure Configuration

Pattern Implementation

This skill references conversation context to determine view structure:

View Type Detection

From conversation context, the skill identifies:

• ViewModel structure (from prior discussion or specifications read by Claude)
• View category: Display-only, interactive, form, or container
• Operations needed: Whether view has user-initiated actions
• Child composition: Whether view binds child views

Component Selection

Based on view type:

• Display-only: ViewModelView protocol, viewModel property only
• Interactive: Add operations, repaintToggle, testDataTransporter, toggleRepaint()
• Form: Add Validations environment, FormFieldView, validation error handling
• Container: Add child view .bind() calls

Code Generation

Generates view file with:

1. ViewModelView protocol conformance
2. Properties (viewModel, operations if needed, repaintToggle if interactive)
3. Body with rendering logic
4. Init storing viewModel and operations
5. Action methods (if interactive)
6. Test infrastructure (if interactive)
7. Previews for different states

Context Sources

Skill references information from:

• Prior conversation: Requirements discussed with user
• Specification files: If Claude has read specifications into context
• ViewModel definitions: From codebase or discussion

Key Patterns

Error Handling Pattern

@State private var error: Error?

var body: some View {
    VStack {
        Button(errorBinding: $error, asyncAction: submit) {
            Text(viewModel.submitLabel)
        }
    }
    .alert(
        errorBinding: $error,
        title: viewModel.errorTitle,
        message: viewModel.errorMessage,
        dismissButtonLabel: viewModel.dismissButtonLabel
    )
}

private func submit() async {
    do {
        try await operations.submit()
    } catch {
        self.error = error
    }
    toggleRepaint()
}

Validation Error Pattern

For forms, handle validation errors separately:

private func submit() async {
    let validations = validations
    do {
        try await operations.submit(data: viewModel.data)
    } catch let error as MyRequest.ResponseError {
        if !error.validationResults.isEmpty {
            validations.replace(with: error.validationResults)
        } else {
            self.error = error
        }
    } catch {
        self.error = error
    }
    toggleRepaint()
}

Async Task Pattern

var body: some View {
    VStack {
        if isLoading {
            ProgressView()
        } else {
            contentView
        }
    }
    .task(errorBinding: $error) {
        try await loadData()
    }
}

private func loadData() async throws {
    isLoading = true
    try await operations.loadData()
    isLoading = false
    toggleRepaint()
}

Conditional Rendering Pattern

Use ViewModel state for conditionals:

var body: some View {
    VStack {
        if viewModel.isEmpty {
            Text(viewModel.emptyStateMessage)
        } else {
            ForEach(viewModel.items) { item in
                ItemRow(item: item)
            }
        }
    }
}

Computed View Components Pattern

Extract reusable view fragments as computed properties:

private var headerView: some View {
    HStack {
        Text(viewModel.title)
        Spacer()
        Image(systemName: viewModel.iconName)
    }
}

var body: some View {
    VStack {
        headerView
        contentView
    }
}

Result/Error Handling Pattern

When a view needs to render multiple possible ViewModels (success, various error types), use an enum wrapper:

The Wrapper ViewModel:

@ViewModel
public struct TaskResultViewModel {
    public enum Result {
        case success(TaskViewModel)
        case notFound(NotFoundViewModel)
        case validationError(ValidationErrorViewModel)
        case permissionDenied(PermissionDeniedViewModel)
    }

    public let result: Result
    public var vmId: ViewModelId = .init(type: Self.self)

    public init(result: Result) {
        self.result = result
    }
}

The View:

public struct TaskResultView: ViewModelView {
    private let viewModel: TaskResultViewModel

    public var body: some View {
        switch viewModel.result {
        case .success(let vm):
            TaskView(viewModel: vm)
        case .notFound(let vm):
            NotFoundView(viewModel: vm)
        case .validationError(let vm):
            ValidationErrorView(viewModel: vm)
        case .permissionDenied(let vm):
            PermissionDeniedView(viewModel: vm)
        }
    }

    public init(viewModel: TaskResultViewModel) {
        self.viewModel = viewModel
    }
}

Key principles:

• Each error scenario has its own ViewModel type
• The wrapper enum associates specific ViewModels with each case
• The view switches on the enum and renders the appropriate child view
• Maintains type safety (no any ViewModel existentials)
• No generic error handling - each error type is specific and meaningful

ViewModelId Initialization - CRITICAL

IMPORTANT: ViewModelId controls SwiftUI's view identity system via the .id(vmId) modifier. Incorrect initialization causes SwiftUI to treat different data as the same view, breaking updates.

❌ WRONG - Never use this:

public var vmId: ViewModelId = .init()  // NO! Generic identity

✅ MINIMUM - Use type-based identity:

public var vmId: ViewModelId = .init(type: Self.self)

This ensures views of the same type get unique identities.

✅ IDEAL - Use data-based identity when available:

public struct TaskViewModel {
    public let id: ModelIdType
    public var vmId: ViewModelId

    public init(id: ModelIdType, /* other params */) {
        self.id = id
        self.vmId = .init(id: id)  // Ties view identity to data identity
        // ...
    }
}

Why this matters:

• SwiftUI uses .id() modifier to determine when to recreate vs update views
• vmId provides this identity for ViewModelViews
• Wrong identity = views don't update when data changes
• Data-based identity (.init(id:)) is best because it ties view lifecycle to data lifecycle

File Organization

Sources/{ViewsTarget}/
├── {Feature}/
│   ├── {Feature}View.swift             # Full page → {Feature}ViewModel
│   ├── {Entity}CardView.swift          # Child component → {Entity}CardViewModel
│   ├── {Entity}RowView.swift           # Child component → {Entity}RowViewModel
│   └── {Modal}View.swift               # Modal → {Modal}ViewModel
├── Shared/
│   ├── HeaderView.swift                # Shared components
│   └── FooterView.swift
└── Styles/
    └── ButtonStyles.swift              # Reusable button styles

Common Mistakes

Computing Data in Views

// ❌ BAD - View is transforming data
var body: some View {
    Text("\(viewModel.firstName) \(viewModel.lastName)")
}

// ✅ GOOD - ViewModel provides shaped result
var body: some View {
    Text(viewModel.fullName)  // via @LocalizedCompoundString
}

Forgetting to Call toggleRepaint()

// ❌ BAD - Test infrastructure won't work
private func submit() {
    operations.submit()
    // Missing toggleRepaint()!
}

// ✅ GOOD - Always call after operations
private func submit() {
    operations.submit()
    toggleRepaint()
}

Using Computed Properties for Display

// ❌ BAD - View is computing
var body: some View {
    if !viewModel.items.isEmpty {
        Text("You have \(viewModel.items.count) items")
    }
}

// ✅ GOOD - ViewModel provides the state
var body: some View {
    if viewModel.hasItems {
        Text(viewModel.itemCountMessage)
    }
}

Hardcoding Text

// ❌ BAD - Not localizable
Button(action: submit) {
    Text("Submit")
}

// ✅ GOOD - ViewModel provides localized text
Button(action: submit) {
    Text(viewModel.submitButtonLabel)
}

Missing Error Binding

// ❌ BAD - Errors not handled
Button(action: submit) {
    Text(viewModel.submitLabel)
}

// ✅ GOOD - Error binding for async actions
Button(errorBinding: $error, asyncAction: submit) {
    Text(viewModel.submitLabel)
}

Storing Operations in Body Instead of Init

// ❌ BAD - Recomputed on every render
public var body: some View {
    let operations = viewModel.operations
    Button(action: { operations.submit() }) {
        Text(viewModel.submitLabel)
    }
}

// ✅ GOOD - Store in init
private let operations: MyOperations

public init(viewModel: MyViewModel) {
    self.viewModel = viewModel
    self.operations = viewModel.operations
}

Mismatched Filenames

// ❌ BAD - Filename doesn't match ViewModel
ViewModel: TaskListViewModel
View:      TasksView.swift

// ✅ GOOD - Aligned names
ViewModel: TaskListViewModel
View:      TaskListView.swift

Incorrect ViewModelId Initialization

// ❌ BAD - Generic identity, views won't update correctly
public var vmId: ViewModelId = .init()

// ✅ MINIMUM - Type-based identity
public var vmId: ViewModelId = .init(type: Self.self)

// ✅ IDEAL - Data-based identity (when id available)
public init(id: ModelIdType) {
    self.id = id
    self.vmId = .init(id: id)
}

Force-Unwrapping Localizable Strings

// ❌ BAD - Force-unwrapping to work around missing overload
import SwiftUI

Text(try! viewModel.title.localizedString)  // Anti-pattern - don't do this!
Label(try! viewModel.label.localizedString, systemImage: "star")

// ✅ GOOD - Request the proper SwiftUI overload instead
// The correct solution is to add an init extension like this:
extension Text {
    public init(_ localizable: Localizable) {
        self.init(localizable.localized)
    }
}

extension Label where Title == Text, Icon == Image {
    public init(_ title: Localizable, systemImage: String) {
        self.init(title.localized, systemImage: systemImage)
    }
}

// Then views use it cleanly without force-unwraps:
Text(viewModel.title)
Label(viewModel.label, systemImage: "star")

Why this matters:

FOSMVVM provides the Localizable protocol for all localized strings and includes SwiftUI init overloads for common elements like Text. However, not every SwiftUI element has a Localizable overload yet.

When you encounter a SwiftUI element that doesn't accept Localizable directly:

1. DON'T work around it with try! localizable.localizedString - this bypasses the type system and spreads force-unwrap calls throughout the view code
2. DO request that we add the proper init overload to FOSUtilities for that SwiftUI element
3. The pattern is simple: Extensions that accept Localizable and pass .localized to the standard initializer

This approach keeps the codebase clean, type-safe, and eliminates force-unwraps from view code entirely.

File Templates

See reference.md for complete file templates.

Naming Conventions

Common Modifiers

FOSMVVM-Specific Modifiers

// Error alert with ViewModel strings
.alert(
    errorBinding: $error,
    title: viewModel.errorTitle,
    message: viewModel.errorMessage,
    dismissButtonLabel: viewModel.dismissButtonLabel
)

// Async task with error handling
.task(errorBinding: $error) {
    try await loadData()
}

// Async submit handler
.onAsyncSubmit {
    await submit()
}

// Test data transporter (DEBUG only)
.testDataTransporter(viewModelOps: operations, repaintToggle: $repaintToggle)

// UI testing identifier
.uiTestingIdentifier("submitButton")

Standard SwiftUI Modifiers

Apply standard modifiers as needed for layout, styling, etc.

How to Use This Skill

Invocation:

/fosmvvm-swiftui-view-generator

Prerequisites:

• ViewModel and its structure are understood from conversation
• Optionally, specification files have been read into context
• View requirements (display-only, interactive, form, container) are clear from discussion

Output:

• {ViewName}View.swift - SwiftUI view conforming to ViewModelView protocol

Workflow integration: This skill is typically used after discussing requirements or reading specification files. The skill references that context automatically—no file paths or Q&A needed.

See Also

• Architecture Patterns - Mental models and patterns
• FOSMVVMArchitecture.md - Full FOSMVVM architecture
• fosmvvm-viewmodel-generator - For creating ViewModels
• fosmvvm-ui-tests-generator - For creating UI tests
• reference.md - Complete file templates

Version History