Box 2.0

Box 2.0

LangLanguage SwiftSwift
License MIT
ReleasedLast Release Oct 2015
SPMSupports SPM

Maintained by Ash Furrow, Gordon Fontenot.

Box 2.0

  • By
  • Rob Rix


This is a Swift microframework which implements Box<T> & MutableBox<T>, with implementations of ==/!= where T: Equatable.

Box is typically used to work around limitations of value types:

  • recursive structs/enums
  • type-parameterized enums where more than one case has a value


Wrapping & unwrapping a Box:

// Wrap:
let box = Box(1)

// Unwrap:
let value = box.value

Changing the value of a MutableBox:

// Mutation:
let mutableBox = MutableBox(1)
mutableBox.value = 2

Building a recursive value type:

struct BinaryTree {
    let value: Int
    let left: Box<BinaryTree>?
    let right: Box<BinaryTree>?

Building a parameterized enum:

enum Result<T> {
    case Success(Box<T>)
    case Failure(NSError)

See the sources for more details.


  1. Add this repo as a submodule in e.g. External/Box:

    git submodule add External/Box
  2. Drag Box.xcodeproj into your .xcworkspace/.xcodeproj.
  3. Add Box.framework to your target’s Link Binary With Libraries build phase.
  4. You may also want to add a Copy Files phase which copies Box.framework (and any other framework dependencies you need) into your bundle’s Frameworks directory. If your target is a framework, you may instead want the client app to include Box.framework.