Bootstrap Guide

Comprehensive guide to safely and efficiently initializing your dependency injection container at app startup. WeaveDI provides powerful bootstrap patterns supporting Swift 5/6 concurrency, test isolation, conditional initialization, and production-ready configuration patterns.

Overview

Core Goals

• 🎧 Centralized Setup: Initialize all dependencies in one place at app startup
• 🔒 Type Safety: Compile-time dependency verification
• ⚡ Performance: Optimized container initialization
• 🧪 Testing: Isolated test environments

Key Features

• 🔄 Concurrency Support: Full async/await and Swift 6 strict concurrency
• 🎯 Atomic Operations: Thread-safe container replacement
• 🔍 Environment Awareness: Different setups for dev/staging/production
• 🧬 Test Isolation: Clean slate for each test

Swift Version Compatibility

Feature	Swift 5.8+	Swift 5.9+	Swift 6.0+
Basic Bootstrap	✅	✅	✅
Async Bootstrap	✅	✅	✅
Mixed Bootstrap	✅	✅	✅
Actor Isolation	⚠️	✅	✅
Strict Sendable	❌	⚠️	✅

When to Use Bootstrap

Required Scenarios

• 🚀 App Launch: Always bootstrap at app startup
• 🧪 Unit Tests: Bootstrap before each test suite
• 🔄 Integration Tests: Bootstrap with test-specific configuration
• 🛠️ Environment Changes: Re-bootstrap when switching environments

Application Entry Points

SwiftUI App (Recommended)

@main
struct MyApp: App {
    init() {
        Task {
            await bootstrapDependencies()
        }
    }

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

UIKit App

class AppDelegate: UIResponder, UIApplicationDelegate {
    func application(_ application: UIApplication,
                   didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        Task {
            await bootstrapDependencies()
        }
        return true
    }
}

Synchronous Bootstrap

import WeaveDI

await WeaveDI.Container.bootstrap { container in
    container.register(Logger.self) { ConsoleLogger() }
    container.register(Networking.self) { DefaultNetworking() }
    container.register(UserRepository.self) { UserRepositoryImpl() }
}

// After bootstrap, use WeaveDI.Container.shared.resolve(...) anywhere
let logger = WeaveDI.Container.shared.resolve(Logger.self)

Asynchronous Bootstrap

Use bootstrapAsync when async initialization is needed (e.g., remote config, database connection).

let ok = await WeaveDI.Container.bootstrapAsync { container in
    // Example: Load remote configuration
    let config = try await RemoteConfig.load()
    container.register(AppConfig.self) { config }

    // Example: Initialize async resources
    let db = try await Database.open()
    container.register(Database.self) { db }
}

guard ok else { /* Handle failure (splash/alert/retry) */ return }

Note: bootstrapAsync can be configured to fatalError in DEBUG builds and return false in RELEASE builds on failure. Current implementation provides Bool return with internal logging.

Mixed Bootstrap (sync + async)

Useful when you want core dependencies immediately and supplementary dependencies asynchronously.

@MainActor
await WeaveDI.Container.bootstrapMixed(
    sync: { container in
        container.register(Logger.self) { ConsoleLogger() }
        container.register(Networking.self) { DefaultNetworking() }
    },
    async: { container in
        // Async extended dependencies
        let analytics = await AnalyticsClient.make()
        container.register(AnalyticsClient.self) { analytics }
    }
)

Bootstrap in Background Task

When you want to minimize app launch delay, perform async bootstrap in background.

WeaveDI.Container.bootstrapInTask { container in
    let featureFlags = try await FeatureFlags.fetch()
    container.register(FeatureFlags.self) { featureFlags }
}

Conditional Bootstrap

Use when you want to skip if already initialized.

let didInit = await WeaveDI.Container.bootstrapIfNeeded { container in
    container.register(Logger.self) { ConsoleLogger() }
}

if !didInit {
    // Already initialized
}

Async version is also available:

let didInit = await WeaveDI.Container.bootstrapAsyncIfNeeded { container in
    let remote = try await RemoteConfig.load()
    container.register(RemoteConfig.self) { remote }
}

Ensure Bootstrapped (Assert)

Use to enforce that bootstrap occurred before DI access.

WeaveDI.Container.ensureBootstrapped() // Precondition failure if not bootstrapped

Testing Guide

Use reset API when you want a clean container for each test.

@MainActor
override func setUp() async throws {
    try await super.setUp()
    await WeaveDI.Container.resetForTesting() // Only allowed in DEBUG builds

    // Test-specific registration
    WeaveDI.Container.shared.register(MockService.self) { MockService() }
}

Best Practices

• Single bootstrap: Call only once at app entry point (or test setUp)
• Handle failures: Prepare user experience path when async bootstrap fails
• Use mixed pattern: Register essential dependencies synchronously, supplementary asynchronously
• Ensure access: Use ensureBootstrapped() in development to catch mistakes early
• Test isolation: Call resetForTesting() before each test