Swift: Practitioner

What to look for:

• Protocol conformance is explicit: struct Dog: Animal — unlike Go's implicit satisfaction
• Protocol extension: add a default implementation in extension MyProtocol { ... }
• Protocol composition: func process(_ item: Drawable & Saveable) — requires both
• Equatable/Hashable auto-synthesised for structs/enums with all-equatable properties

What to look for:

• <T: Equatable> constrains T to types that support == comparison
• some View: opaque — compiler knows the concrete type; zero boxing cost (used in SwiftUI)
• any Drawable: existential — runtime type erasure; enables heterogeneous collections
• associated type in protocols: placeholder type resolved by conforming type

What to look for:

• throws: marks a function that can fail — callers must handle with try
• try? converts a thrown error to nil — use when you don't care about the specific error
• try! crashes on error — use only when failure is truly impossible
• do-catch must catch all thrown types — or add a catch { } catch-all at the end

What to look for:

• compactMap: like map but discards nil results — great for optional transformation
• Dictionary access returns Optional: dict["key"] returns String? — may be nil if missing
• Set: unordered, unique elements — O(1) contains, union, intersection, subtract
• lazy: .lazy.filter{...}.map{...} — doesn't compute until iterated; efficient for large sequences

What to look for:

• struct User: Codable — synthesised automatically if all properties are Codable
• CodingKeys enum maps Swift property names to JSON keys (camelCase ↔ snake_case)
• JSONDecoder().keyDecodingStrategy = .convertFromSnakeCase — auto-maps without CodingKeys
• Nested Codable types work automatically — the compiler recurses through the structure