Swift Style

Weighing Late Property Declaration

There’s a dedicated movement of Swift coders who prefer to add constant and variable declarations at the end of a type implementation rather than the start. Here’s an example from the Swift standard library. It’s a fairly long example that highlights a subtle declaration layout style. Look at the two internal let declarations at the end of this structure:

public struct Zip2Sequence<
  Sequence1 : Sequence, Sequence2 : Sequence>
  : Sequence {

  public typealias Stream1 = Sequence1.Iterator
  public typealias Stream2 = Sequence2.Iterator

  /// A type whose instances can produce the elements of this
  /// sequence, in order.
  public typealias Iterator = Zip2Iterator ...