Swift Language Standards

Priority: P0

Implementation Guidelines

Optionals & Safety

• Never Force Unwrap: Use guard let, if let, or nil coalescing (??) to safely unwrap.
• Nil Comparison: Use

  value != nil

  instead of

  if let _ = value

  .
• Implicitly Unwrapped: Avoid

  Type!

  . Use proper

  Type?

  .

Protocols & Extensions

• Protocols as Blueprints: Protocols define a blueprint; classes inherit implementation.
• Composition over Inheritance: Prefer protocol composition with structs for better decoupling and performance.
• Extensions: Implement conformance in an extension:

  extension MyType: MyProtocol { ... }

  . Use extensions for clean code organization, not storage (do not use extensions for stored properties).
• Protocol Witnesses: Explicitly implement all required members to satisfy the witness table.

Type Safety

• Avoid

  Any

  : Use generics or associated types instead for compile-time safety.
• Enums: Prefer enums with associated values over multiple Optionals. Extract values via a switch statement (e.g.,

  case .success(let value):

  ).
• Value Types: Default to struct for value semantics and thread safety. Use

  class

  only when reference identity is necessary or for inheritance. Structs are copied; classes are shared.

Anti-Patterns

• No ! operator: Use safe unwrapping.
• No -1 for failure: Use Optional.
• No force cast (as!): Use conditional cast (as?).

References

• Optionals & Protocols