Swift Best Practices

Priority: P0

Implementation Guidelines

Control Flow (Guard over If)

• 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 the top of a 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.

Value Types & Immutability

• Prefer Structs: Default to struct for value semantics and thread safety. Use

  class

  only when reference identity or inheritance is required.
• Immutability: Always default to let for all properties and constants. Use

  var

  only when change is required.
• Modifiers: Use

  final

  for all classes that are not intended to be subclassed to improve performance (static dispatch).
• Static Dispatch: Favor methods in structs and

  final

  classes.

Naming & Style

• Clear Intent: Prefix booleans with

  is, has, or can

  . Example:

  isValid

  ,

  hasErrors

  ,

  canEdit

  . Makes boolean state clear.
• API Guidelines: Follow the 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 the underlying type is internal.

Collection Performance

• Sequence API: Use

  compactMap

  ,

  filter

  , and

  reduce

  instead of explicit for-where loops for data transformations.
• Lazy Collections: Use

  .lazy

  for large sequences when the result is consumed partially.
• Dictionaries: Use

  default

  values in dictionary access to avoid double optional unwrapping.

Anti-Patterns

• 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.

References

• Guard Patterns & Immutability