FOSMVVM SwiftUI App Setup

Generate the main App struct for a SwiftUI application using FOSMVVM architecture.

Conceptual Foundation

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

The App struct is the entry point of a SwiftUI application. In FOSMVVM, it has three core responsibilities:

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Core Components

1. MVVMEnvironment

The MVVMEnvironment provides FOSMVVM infrastructure to all views:

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Key configuration:

• - appBundle - Usually Bundle.main (the app bundle)
• INLINECODE3 - Array of localization bundles from your modules
• INLINECODE4 - URLs for each deployment environment

Resource Bundle Accessors:

Each module that contains localization resources should provide a bundle accessor:

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This pattern:

• - Uses Bundle.module which SPM automatically provides for each module
• Provides a clean public API for accessing the module's resources
• Keeps bundle access centralized in one place per module

2. Environment Injection

The MVVMEnvironment is injected at the WindowGroup level:

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This makes the environment available to all views in the hierarchy.

3. Test Infrastructure

The test infrastructure enables UI testing with specific configurations:

.testHost { } modifier:
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Key points:

• - Apply to the top-level view in WindowGroup (the outermost view in your hierarchy)
• This ensures the modifier wraps the entire view hierarchy to intercept test configurations
• Always include the default: case
• The default case detects test mode via process arguments
• Sets @State private var underTest = false flag
• Optional: Add specific test configurations for advanced scenarios

registerTestingViews() function:
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Key points:

• - Extension on the App struct (not MVVMEnvironment)
• Called from INLINECODE11
• Registers every ViewModelView for isolated testing
• DEBUG only

When to Use This Skill

• - Starting a new FOSMVVM SwiftUI application
• Migrating an existing SwiftUI app to FOSMVVM
• Setting up the App struct with proper FOSMVVM infrastructure
• Configuring test infrastructure for UI testing

What This Skill Generates

Component	Location	Purpose
Main App struct	INLINECODE12	Entry point with MVVMEnvironment setup
MVVMEnvironment configuration

Computed property in App struct | Bundles and deployment URLs | | Test infrastructure | DEBUG blocks in App struct | UI testing support |

Project Structure Configuration

Placeholder	Description	Example
INLINECODE13	Your app name	INLINECODE14, INLINECODE15
INLINECODE16

Main app target | App | | {ResourceBundles} | Module names with localization | MyAppViewModels, SharedResources |

How to Use This Skill

Invocation:
/fosmvvm-swiftui-app-setup

Prerequisites:

• - App name understood from conversation context
• Deployment URLs discussed or documented
• Resource bundles identified (modules with localization)
• Test support requirements clarified

Workflow integration:
This skill is used when setting up a new FOSMVVM SwiftUI application or adding FOSMVVM infrastructure to an existing app. The skill references conversation context automatically—no file paths or Q&A needed.

Pattern Implementation

This skill references conversation context to determine App struct configuration:

Configuration Detection

From conversation context, the skill identifies:

• - App name (from project discussion or existing code)
• Deployment environments (production, staging, debug URLs)
• Resource bundles (modules containing localization YAML files)
• Test infrastructure (whether UI testing support needed)

MVVMEnvironment Setup

Based on project structure:

• - App bundle (typically Bundle.main)
• Resource bundle accessors (from identified modules)
• Deployment URLs (for each environment)
• Current version (from shared module)

Test Infrastructure Planning

If test support needed:

• - Test detection (process arguments check)
• Test host modifier (wrapping top-level view)
• View registration (all ViewModelViews for testing)

File Generation

1. 1. Main App struct with @main attribute
2. MVVMEnvironment computed property
3. WindowGroup with environment injection
4. Test infrastructure (if requested, DEBUG-only)
5. registerTestingViews() extension (if test support)

Context Sources

Skill references information from:

• - Prior conversation: App requirements, deployment environments discussed
• Project structure: From codebase analysis of module organization
• Existing patterns: From other FOSMVVM apps if context available

Key Patterns

MVVMEnvironment as Computed Property

The MVVMEnvironment is a computed property, not a stored property:

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Why computed?

• - Keeps initialization logic separate
• Can be customized in DEBUG vs RELEASE
• Clear dependency on bundles and URLs

Test Detection Pattern

The default test detection uses process arguments:

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Why this approach?

• - Simple and reliable for DEBUG builds
• No additional dependencies
• Process arguments are set by test runner

Register All ViewModelViews

Every ViewModelView should be registered for testing:

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Organization tips:

• - Group by feature/screen with comments
• Alphabetical order within groups
• One view per line for easy scanning

Common Customizations

Multiple Environment Values

You can inject multiple environment values:

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Conditional Test Registration

You can conditionally register views based on build configuration:

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Advanced Test Configurations

You can add specific test configurations in .testHost:

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File Templates

See reference.md for complete file templates.

Naming Conventions

Concept	Convention	Example
App struct	INLINECODE23	INLINECODE24, INLINECODE25
Main file

{Name}App.swift | MyApp.swift | | MVVMEnvironment property | mvvmEnv | Always mvvmEnv | | Test flag | underTest | Always underTest |

Deployment Configuration

FOSMVVM supports deployment detection via Info.plist:

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Local development override:

• - Edit Scheme → Run → Arguments → Environment Variables
• Add: INLINECODE32

See Also

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

Version History

Version	Date	Changes
1.0	2026-01-23	Initial skill for SwiftUI app setup
1.1

2026-01-24 | Update to context-aware approach (remove file-parsing/Q&A). Skill references conversation context instead of asking questions or accepting file paths. |