# Swiftui Advanced

> Use when implementing gesture composition (simultaneous, sequenced, exclusive), adaptive layouts…

Use when implementing gesture composition (simultaneous, sequenced, exclusive), adaptive layouts (ViewThatFits, AnyLayout, size classes), or choosing architecture patterns (MVVM vs TCA vs vanilla, State-as-Bridge). Covers advanced SwiftUI patterns beyond basic views.

- Page: https://ss33.ai/skills/johnrogers/swiftui-advanced-8811241239
- Publisher: johnrogers
- Category: [Software Development](https://ss33.ai/skills/category/software-development-t44z8z) › [Mobile apps](https://ss33.ai/skills/category/software-development-t44z8z/mobile-apps-p8puwc)
- License: MIT
- Source: https://github.com/johnrogers/claude-swift-engineering/blob/1dc2cf4d020bd524168f20bec95104da6cb2888c/plugins/swift-engineering/skills/swiftui-advanced/SKILL.md

## Skill

SKILL.md: https://ss33.ai/api/v1/ss33/download/johnrogers/swiftui-advanced-8811241239

# SwiftUI Advanced

Advanced SwiftUI patterns for gesture composition, adaptive layouts, architecture decisions, and performance optimization.

## Reference Loading Guide

**ALWAYS load reference files if there is even a small chance the content may be required.** It's better to have the context than to miss a pattern or make a mistake.

| Reference | Load When |
|-----------|-----------|
| **[Gestures](references/gestures.md)** | Composing multiple gestures, GestureState, custom recognizers |
| **[Adaptive Layout](references/adaptive-layout.md)** | ViewThatFits, AnyLayout, size classes, iOS 26 free-form windows |
| **[Architecture](references/architecture.md)** | MVVM vs TCA decision, State-as-Bridge, property wrapper selection |
| **[Performance](references/performance.md)** | Instruments 26, view body optimization, unnecessary updates |

## Core Workflow

1. **Identify pattern category** from user's question
2. **Load relevant reference** for detailed patterns and code examples
3. **Apply pattern** following the decision trees and anti-patterns
4. **Verify** using provided checklists or profiling guidance

## Decision Trees

### Gesture Composition
- Both gestures at same time? -> `.simultaneously`
- One must complete before next? -> `.sequenced`
- Only one should win? -> `.exclusively`

### Layout Adaptation
- Pick best-fitting variant? -> `ViewThatFits`
- Animated H/V switch? -> `AnyLayout`
- Need actual dimensions? -> `onGeometryChange`

### Architecture Selection
- Small app, Apple patterns? -> @Observable + State-as-Bridge
- Complex presentation logic? -> MVVM with @Observable
- Rigorous testability needed? -> TCA

## Common Mistakes

1. **Gesture composition order matters** — `.simultaneously` and `.sequenced` have different trigger timing. Swapping them silently changes behavior. Understand gesture semantics before using.

2. **ViewThatFits over-used** — ViewThatFits remeasures on every view change. For animated H/V switches, use `AnyLayout` instead. Use ViewThatFits only for static variant selection.

3. **onGeometryChange triggering unnecessary updates** — Reading geometry changes geometry, which triggers updates, which changes geometry... circular. Use `.onGeometryChange` only with proper state management to avoid loops.

4. **Architecture mismatch mid-project** — Starting with @Observable + State-as-Bridge then realizing you need TCA is expensive. Choose architecture upfront based on complexity (small app = @Observable, complex = TCA).

5. **Ignoring view body optimization** — Computing expensive calculations in view body repeatedly kills performance. Move calculations to properties or models. Profile with Instruments 26 before optimizing prematurely.