SwiftUI .task() vs .onAppear() Demo

A practical SwiftUI demonstration app that showcases the differences between .task() and .onAppear() view modifiers through a live cat facts streaming example.

📖 About

This project accompanies the article "Understanding When to Use .task() vs .onAppear in SwiftUI" published on Clement's Substack.

✨ Features

• Live Cat Facts Stream: Demonstrates .task() modifier with continuous data streaming
• Automatic Task Management: Shows automatic cancellation when view disappears
• AsyncStream Implementation: Real-world example of async/await in SwiftUI
• Clean Architecture: Simple, educational code structure

🚀 What You'll Learn

.onAppear() - Standard View Modifier

• Performs synchronous actions when a view appears
• One-time setup operations
• Cannot handle async/await directly

.task() - Async-Aware View Modifier

• Handles asynchronous operations seamlessly
• Task lifetime tied to view lifecycle
• Automatic cancellation when view disappears
• Support for task priorities
• Built-in memory management

🔧 How It Works

The app demonstrates a practical use case where:

1. Home View: Simple navigation starting point
2. Live Facts View: Streams cat facts every 2 seconds using .task()
3. Automatic Cleanup: When navigating away, the async task automatically cancels

.task {
    for await newFact in catFactStream() {
        withAnimation {
            fact = newFact
        }
    }
}

🏃‍♂️ Running the Project

1. Clone this repository
2. Open onAppear.xcodeproj in Xcode
3. Build and run on iOS Simulator or device
4. Navigate to "Show Live Cat Facts" to see .task() in action

📚 Key Takeaways

• Use .onAppear() for simple, synchronous setup tasks
• Use .task() for async operations, network requests, and long-running processes
• .task() provides better resource management and automatic cleanup
• Task priorities help optimize performance in complex apps

🔗 Learn More

Read the full article: Understanding When to Use .task() vs .onAppear in SwiftUI

📱 Requirements

• iOS 15.0+
• Xcode 13.0+
• Swift 5.5+

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This project demonstrates modern SwiftUI patterns and Swift concurrency features for educational purposes.