Value Types First

Default to structs for data models. Use classes only when you need reference semantics: identity comparisons, inheritance, delegate patterns, or Objective-C interop.

// Prefer: value type for data
struct UserProfile {
    var name: String
    var email: String
}

// Class when reference semantics are needed
class SessionManager {
    static let shared = SessionManager()
    private init() {}
}

Enums with associated values replace class hierarchies for modeling finite states.