swift-best-practices

Swift Best Practices

Priority: P0 (CRITICAL)

Guard for Early Exit: Use guard let over nested if statements for better readability and to unwrap optionals early.
Nested Checks: Use guard for precondition checks at top of function to reduce nested depth.
Switch Exhaustiveness: Always handle all cases; use @unknown default for freezing enums (enums from frameworks).
if-case: Use if case .success(let value) = result for simple enum pattern matching.

Prefer Structs: Default to struct for value semantics and thread safety. Use class only when reference identity or inheritance required.
Immutability: Always default to let for all properties and constants. Use var only when change required.
Modifiers: Use final for all classes that not intended to subclassed to improve performance (static dispatch).
Static Dispatch: Favor methods in structs and final classes.

Clear Intent: Prefix booleans with is, has, or can. Example: isValid, hasErrors, canEdit. Makes boolean state clear.
API Guidelines: Follow official Swift API Design Guidelines. Use camelCase for clear names and PascalCase for types.
Protocols: Name protocols with -able, -ible, or -ing suffixes (e.g., Codable, Identifiable).
Opaque Types: Use some View or some Collection for return types where underlying type internal.

Sequence API: Use compactMap, filter, and reduce instead of explicit for-where loops for data transformations.
Lazy Collections: Use .lazy for large sequences when result consumed partially.
Dictionaries: Use default values in dictionary access to avoid double optional unwrapping.

No Pyramid of Doom: Use guard for early exits.
No force unwrap: Never use ! on optionals. Use ?? (nil-coalescing) or if let.
No global var: Avoid mutable global state. Use Singletons (accessed via static let shared) or DI.