UIKit Guide

Applies to: UIKit (iOS 12+), Swift 5.0+, Imperative UI, iOS/tvOS/Mac Catalyst

Core Principles

1. MVVM + Coordinator: Separate view logic (VC), presentation (ViewModel), and navigation (Coordinator)
2. Programmatic UI: Build views in code with Auto Layout; avoid storyboards for team projects
3. Thin View Controllers: View controllers configure views and bind to view models; no business logic
4. Protocol-Oriented Delegation: Use delegate protocols for callbacks; always declare delegates weak
5. Memory Safety: Use [weak self] in closures, cancel tasks in deinit, break retain cycles

Guardrails

View Controller Rules

• Keep view controllers under 200 lines (extract views, helpers, extensions)
• Override viewDidLoad once; call setupUI(), setupConstraints(), setupBindings()
• Never put networking or business logic in view controllers