Swift 6.2 Approachable Concurrency Guide

Expert guidance on Swift's concurrency system for iOS 26+ apps.

Core Mental Model: The Office Building

Think of your app as an office building where isolation domains are private offices with locks:

• MainActor = Front desk (handles all UI interactions, only one exists)
• actor types = Department offices (each protects its own data)
• nonisolated code = Hallways (shared space, no private documents)
• Sendable types = Photocopies (safe to share between offices)
• Non-Sendable types = Original documents (must stay in one office)

You can't barge into someone's office. You knock (await) and wait.

The Core Shift: "Stay on the Caller"