1.
Swift
(via swift-2048)
Austin Zheng

2.
Who am I?
• My name is Austin Zheng
• I work at LinkedIn as an iOS developer
• Before that I wrote firmware for an embedded
systems startup in Redwood City

3.
What Is 2048?
• iOS clone of web game “2048” by
Gabriele Cirulli
• In turn based on iOS game “Threes”
by Asher Vollmer
• Slide in a direction to combine like
tiles
• 2+2 = 4, 4+4 = 8
• Make a ‘2048’ tile, or fill up the
board and lose

4.
(2048 demo)

5.
Architecture
(very high level)
View
Game Logic
(Model)
View Controller
Actions
View Commands
(forwarded to view)
Backing
Store

6.
Backing Store

7.
Backing Store (Old)
@interface F3HGameModel ()
@property (nonatomic, strong) NSMutableArray *gameState;
@property (nonatomic) NSUInteger dimension;
//...
@end

8.
Backing Store
struct SquareGameboard<T> {
var boardArray: [T]; let dimension: Int
!
init(dimension d: Int, initialValue: T) {
dimension = d
boardArray = [T](count:d*d, repeatedValue:initialValue)
}
!
subscript(row: Int, col: Int) -> T {
get {
return boardArray[row*dimension + col]
}
set {
boardArray[row*dimension + col] = newValue
}
}
}

9.
Structs
• Like classes, they can have properties and
methods.
• Unlike classes, structs can’t inherit from other
structs.
• Unlike classes, structs are value types

10.
Generics
struct SquareGameboard<T> {
let dimension: Int
var boardArray: [T]
!
init(dimension d: Int, initialValue: T) {
dimension = d
boardArray = [T](count:d*d, repeatedValue:initialValue)
}
}

11.
Subscripts
subscript(row: Int, col: Int) -> T {
get {
return boardArray[row*dimension + col]
}
set {
boardArray[row*dimension + col] = newValue
}
}
gameboard[x, y] = TileObject.Empty
!
let someTile = gameboard[x, y]

12.
What, exactly, are we
storing?

13.
TileModel (Old)
// This is an Objective-C class which represents a tile
@interface F3HTileModel : NSObject
@property (nonatomic) BOOL empty;
@property (nonatomic) NSUInteger value;
@end

14.
TileObject
enum TileObject {
case Empty
case Tile(value: Int)
}
!
let anEmptyTile = TileObject.Empty
let eightTile = TileObject.Tile(value: 8)
let anotherTile = TileObject.Tile(value: 2)

15.
Swift Enums
• They can do everything C or Objective-C enums
can…
• They can also do everything structs in Swift can
do - methods and properties…
• Optionally, you can have an enum value store
associated data. (variants, tagged unions, sum
types, case classes)

16.
Game Logic

17.
22
2
22
2
2

18.
22
2
22
2
2

19.
22
2
22
2
2

20.
func performMove(direction: MoveDirection) -> Bool {
func coordinateGenerator(currentRowOrColumn: Int) -> [(Int, Int)] {
var buffer = Array<(Int, Int)>(count:self.dimension, repeatedValue: (0, 0))
for i in 0..<self.dimension {
switch direction {
case .Up: buffer[i] = (i, currentRowOrColumn)
case .Down: buffer[i] = (self.dimension - i - 1, currentRowOrColumn)
case .Left: buffer[i] = (currentRowOrColumn, i)
case .Right: buffer[i] = (currentRowOrColumn, self.dimension - i - 1)
}
}
return buffer
}
!
for i in 0..<dimension {
let coords = coordinateGenerator(i)
let tiles = coords.map() { (c: (Int, Int)) -> TileObject in
let (x, y) = c
return self.gameboard[x, y]
}
let orders = merge(tiles)
// ...
}
// ...
}

21.
func performMove(direction: MoveDirection) -> Bool {
func coordinateGenerator(currentRowOrColumn: Int) -> [(Int, Int)] {
var buffer = Array<(Int, Int)>(count:self.dimension, repeatedValue: (0, 0))
for i in 0..<self.dimension {
switch direction {
case .Up: buffer[i] = (i, currentRowOrColumn)
case .Down: buffer[i] = (self.dimension - i - 1, currentRowOrColumn)
case .Left: buffer[i] = (currentRowOrColumn, i)
case .Right: buffer[i] = (currentRowOrColumn, self.dimension - i - 1)
}
}
return buffer
}
!
for i in 0..<dimension {
let coords = coordinateGenerator(i)
let tiles = coords.map() { (c: (Int, Int)) -> TileObject in
let (x, y) = c
return self.gameboard[x, y]
}
let orders = merge(tiles)
// ...
}
// ...
}

22.
func performMove(direction: MoveDirection) -> Bool {
func coordinateGenerator(currentRowOrColumn: Int) -> [(Int, Int)] {
var buffer = Array<(Int, Int)>(count:self.dimension, repeatedValue: (0, 0))
for i in 0..<self.dimension {
switch direction {
case .Up: buffer[i] = (i, currentRowOrColumn)
case .Down: buffer[i] = (self.dimension - i - 1, currentRowOrColumn)
case .Left: buffer[i] = (currentRowOrColumn, i)
case .Right: buffer[i] = (currentRowOrColumn, self.dimension - i - 1)
}
}
return buffer
}
!
for i in 0..<dimension {
let coords = coordinateGenerator(i)
let tiles = coords.map() { (c: (Int, Int)) -> TileObject in
let (x, y) = c
return self.gameboard[x, y]
}
let orders = merge(tiles)
// ...
}
// ...
}

23.
func performMove(direction: MoveDirection) -> Bool {
func coordinateGenerator(currentRowOrColumn: Int) -> [(Int, Int)] {
var buffer = Array<(Int, Int)>(count:self.dimension, repeatedValue: (0, 0))
for i in 0..<self.dimension {
switch direction {
case .Up: buffer[i] = (i, currentRowOrColumn)
case .Down: buffer[i] = (self.dimension - i - 1, currentRowOrColumn)
case .Left: buffer[i] = (currentRowOrColumn, i)
case .Right: buffer[i] = (currentRowOrColumn, self.dimension - i - 1)
}
}
return buffer
}
!
for i in 0..<dimension {
let coords = coordinateGenerator(i)
let tiles = coords.map() { (c: (Int, Int)) -> TileObject in
let (x, y) = c
return self.gameboard[x, y]
}
let orders = merge(tiles)
// ...
}
// ...
}

24.
func performMove(direction: MoveDirection) -> Bool {
func coordinateGenerator(currentRowOrColumn: Int) -> [(Int, Int)] {
var buffer = Array<(Int, Int)>(count:self.dimension, repeatedValue: (0, 0))
for i in 0..<self.dimension {
switch direction {
case .Up: buffer[i] = (i, currentRowOrColumn)
case .Down: buffer[i] = (self.dimension - i - 1, currentRowOrColumn)
case .Left: buffer[i] = (currentRowOrColumn, i)
case .Right: buffer[i] = (currentRowOrColumn, self.dimension - i - 1)
}
}
return buffer
}
!
for i in 0..<dimension {
let coords = coordinateGenerator(i)
let tiles = coords.map() { (c: (Int, Int)) -> TileObject in
let (x, y) = c
return self.gameboard[x, y]
}
let orders = merge(tiles)
// ...
}
// ...
}

25.
func performMove(direction: MoveDirection) -> Bool {
func coordinateGenerator(currentRowOrColumn: Int) -> [(Int, Int)] {
var buffer = Array<(Int, Int)>(count:self.dimension, repeatedValue: (0, 0))
for i in 0..<self.dimension {
switch direction {
case .Up: buffer[i] = (i, currentRowOrColumn)
case .Down: buffer[i] = (self.dimension - i - 1, currentRowOrColumn)
case .Left: buffer[i] = (currentRowOrColumn, i)
case .Right: buffer[i] = (currentRowOrColumn, self.dimension - i - 1)
}
}
return buffer
}
!
for i in 0..<dimension {
let coords = coordinateGenerator(i)
let tiles = coords.map() { (c: (Int, Int)) -> TileObject in
let (x, y) = c
return self.gameboard[x, y]
}
let orders = merge(tiles)
// ...
}
// ...
}

26.
A single row…
• Condense the row to remove any space - some
might move, some might stay still
• Collapse two adjacent tiles of equal value into a
single tile with double the value
• Convert our intermediate representation into
‘Actions’ that the view layer can easily act upon

27.
Tracking changes?
• We want to know when a tile is moved, when it
stays still, when it’s combined
• Let’s posit an ActionToken
• An ActionToken lives in an array. Its position in the
array is the final position of the tile it represents
• An ActionToken also tracks the state of the tile or
tiles that undertook the action it describes

28.
ActionToken (old)
typedef enum {
F3HMergeTileModeNoAction = 0,
F3HMergeTileModeMove,
F3HMergeTileModeSingleCombine,
F3HMergeTileModeDoubleCombine
} F3HMergeTileMode;
!
@interface F3HMergeTile : NSObject
@property (nonatomic) F3HMergeTileMode mode;
@property (nonatomic) NSInteger originalIndexA;
@property (nonatomic) NSInteger originalIndexB;
@property (nonatomic) NSInteger value;
!
+ (instancetype)mergeTile;
@end

29.
ActionToken
enum ActionToken {
case NoAction(source: Int, value: Int)
case Move(source: Int, value: Int)
case SingleCombine(source: Int, value: Int)
case DoubleCombine(source: Int, second: Int, value: Int)
}

30.
Game Logic
• Condense - remove spaces between tiles
42
2 4

31.
func condense(group: [TileObject]) -> [ActionToken] {
var tokenBuffer = [ActionToken]()
for (idx, tile) in enumerate(group) {
switch tile {
case let .Tile(value) where tokenBuffer.count == idx:
tokenBuffer.append(ActionToken.NoAction(source: idx, value: value))
case let .Tile(value):
tokenBuffer.append(ActionToken.Move(source: idx, value: value))
default:
break
}
}
return tokenBuffer;
}

32.
func condense(group: [TileObject]) -> [ActionToken] {
var tokenBuffer = [ActionToken]()
for (idx, tile) in enumerate(group) {
switch tile {
case let .Tile(value) where tokenBuffer.count == idx:
tokenBuffer.append(ActionToken.NoAction(source: idx, value: value))
case let .Tile(value):
tokenBuffer.append(ActionToken.Move(source: idx, value: value))
default:
break
}
}
return tokenBuffer;
}

33.
Swift ‘switch’
• At its most basic, works like the C or Objective-C
switch statement
• But it can do far more!
• One example: take the values out of an enum
• Cases can be qualified by ‘where’ clauses
• Has to be comprehensive, and no default
fallthrough

34.
Game Logic
• Collapse - perform necessary merges
4 84
4 2 82

35.
func collapse(group: [ActionToken]) -> [ActionToken] {
func quiescentTileStillQuiescent(inputPosition: Int, outputLength: Int, originalPosition: Int) -> Bool {
return (inputPosition == outputLength) && (originalPosition == inputPosition)
}
!
var tokenBuffer = [ActionToken]()
var skipNext = false
for (idx, token) in enumerate(group) {
if skipNext {
skipNext = false
continue
}
switch token {
case .SingleCombine:
assert(false, "Cannot have single combine token in input")
case .DoubleCombine:
assert(false, "Cannot have double combine token in input")
case let .NoAction(s, v)
where (idx < group.count-1
&& v == group[idx+1].getValue()
&& quiescentTileStillQuiescent(idx, tokenBuffer.count, s)):
let nv = v + group[idx+1].getValue()
skipNext = true
tokenBuffer.append(ActionToken.SingleCombine(source: next.getSource(), value: nv))
case let t where (idx < group.count-1 && t.getValue() == group[idx+1].getValue()):
let next = group[idx+1]
let nv = t.getValue() + group[idx+1].getValue()
skipNext = true
tokenBuffer.append(ActionToken.DoubleCombine(source: t.getSource(), second: next.getSource(), value: nv))
case let .NoAction(s, v) where !quiescentTileStillQuiescent(idx, tokenBuffer.count, s):
tokenBuffer.append(ActionToken.Move(source: s, value: v))
case let .NoAction(s, v):
tokenBuffer.append(ActionToken.NoAction(source: s, value: v))
case let .Move(s, v):
tokenBuffer.append(ActionToken.Move(source: s, value: v))
default:
break
}
}
return tokenBuffer
}

36.
Game Logic
• Convert - create ‘move orders’ for the view
enum MoveOrder {
case SingleMoveOrder(source: Int,
destination: Int,
value: Int,
wasMerge: Bool)
case DoubleMoveOrder(firstSource: Int,
secondSource: Int,
destination: Int,
value: Int)
}

37.
func convert(group: [ActionToken]) -> [MoveOrder] {
var moveBuffer = [MoveOrder]()
for (idx, t) in enumerate(group) {
switch t {
case let .Move(s, v):
moveBuffer.append(MoveOrder.SingleMoveOrder(source: s,
destination: idx, value: v, wasMerge: false))
case let .SingleCombine(s, v):
moveBuffer.append(MoveOrder.SingleMoveOrder(source: s,
destination: idx, value: v, wasMerge: true))
case let .DoubleCombine(s1, s2, v):
moveBuffer.append(MoveOrder.DoubleMoveOrder(firstSource: s1,
secondSource: s2, destination: idx, value: v))
default:
break
}
}
return moveBuffer
}

38.
Views

39.
func insertTile(pos: (Int, Int), value: Int) {
let (row, col) = pos
let x = tilePadding + CGFloat(col)*(tileWidth + tilePadding)
let y = tilePadding + CGFloat(row)*(tileWidth + tilePadding)
let r = (cornerRadius >= 2) ? cornerRadius - 2 : 0
let tile = TileView(position: CGPointMake(x, y),
width: tileWidth, value: value, radius: r, delegate: provider)
tile.layer.setAffineTransform(CGAffineTransformMakeScale(tilePopStartScale,
tilePopStartScale))
!
addSubview(tile)
bringSubviewToFront(tile)
UIView.animateWithDuration(tileExpandTime,
delay: tilePopDelay,
options: UIViewAnimationOptions.TransitionNone,
animations: { () -> Void in
// Make the tile 'pop'
tile.layer.setAffineTransform(CGAffineTransformMakeScale(self.tilePopMaxScale,
self.tilePopMaxScale))
},
completion: { (finished: Bool) -> Void in
// Shrink the tile after it 'pops'
UIView.animateWithDuration(self.tileContractTime, animations: { () -> Void in
tile.layer.setAffineTransform(CGAffineTransformIdentity)
})
})
}

40.
func insertTile(pos: (Int, Int), value: Int) {
let (row, col) = pos
let x = tilePadding + CGFloat(col)*(tileWidth + tilePadding)
let y = tilePadding + CGFloat(row)*(tileWidth + tilePadding)
let r = (cornerRadius >= 2) ? cornerRadius - 2 : 0
let tile = TileView(position: CGPointMake(x, y),
width: tileWidth, value: value, radius: r, delegate: provider)
tile.layer.setAffineTransform(CGAffineTransformMakeScale(tilePopStartScale,
tilePopStartScale))
!
addSubview(tile)
bringSubviewToFront(tile)
UIView.animateWithDuration(tileExpandTime,
delay: tilePopDelay,
options: UIViewAnimationOptions.TransitionNone,
animations: { () -> Void in
// Make the tile 'pop'
tile.layer.setAffineTransform(CGAffineTransformMakeScale(self.tilePopMaxScale,
self.tilePopMaxScale))
},
completion: { (finished: Bool) -> Void in
// Shrink the tile after it 'pops'
UIView.animateWithDuration(self.tileContractTime, animations: { () -> Void in
tile.layer.setAffineTransform(CGAffineTransformIdentity)
})
})
}

41.
func insertTile(pos: (Int, Int), value: Int) {
let (row, col) = pos
let x = tilePadding + CGFloat(col)*(tileWidth + tilePadding)
let y = tilePadding + CGFloat(row)*(tileWidth + tilePadding)
let r = (cornerRadius >= 2) ? cornerRadius - 2 : 0
let tile = TileView(position: CGPointMake(x, y),
width: tileWidth, value: value, radius: r, delegate: provider)
tile.layer.setAffineTransform(CGAffineTransformMakeScale(tilePopStartScale,
tilePopStartScale))
!
addSubview(tile)
bringSubviewToFront(tile)
UIView.animateWithDuration(tileExpandTime,
delay: tilePopDelay,
options: UIViewAnimationOptions.TransitionNone,
animations: { () -> Void in
// Make the tile 'pop'
tile.layer.setAffineTransform(CGAffineTransformMakeScale(self.tilePopMaxScale,
self.tilePopMaxScale))
},
completion: { (finished: Bool) -> Void in
// Shrink the tile after it 'pops'
UIView.animateWithDuration(self.tileContractTime, animations: { () -> Void in
tile.layer.setAffineTransform(CGAffineTransformIdentity)
})
})
}

42.
func insertTile(pos: (Int, Int), value: Int) {
let (row, col) = pos
let x = tilePadding + CGFloat(col)*(tileWidth + tilePadding)
let y = tilePadding + CGFloat(row)*(tileWidth + tilePadding)
let r = (cornerRadius >= 2) ? cornerRadius - 2 : 0
let tile = TileView(position: CGPointMake(x, y),
width: tileWidth, value: value, radius: r, delegate: provider)
tile.layer.setAffineTransform(CGAffineTransformMakeScale(tilePopStartScale,
tilePopStartScale))
!
addSubview(tile)
bringSubviewToFront(tile)
UIView.animateWithDuration(tileExpandTime,
delay: tilePopDelay,
options: UIViewAnimationOptions.TransitionNone,
animations: { () -> Void in
// Make the tile 'pop'
tile.layer.setAffineTransform(CGAffineTransformMakeScale(self.tilePopMaxScale,
self.tilePopMaxScale))
},
completion: { (finished: Bool) -> Void in
// Shrink the tile after it 'pops'
UIView.animateWithDuration(self.tileContractTime, animations: { () -> Void in
tile.layer.setAffineTransform(CGAffineTransformIdentity)
})
})
}

43.
Selectors
UISwipeGestureRecognizer *upSwipe = [[UISwipeGestureRecognizer alloc]
initWithTarget:self action:@selector(upButtonTapped)];
!
upSwipe.numberOfTouchesRequired = 1;
upSwipe.direction = UISwipeGestureRecognizerDirectionUp;
[self.view addGestureRecognizer:upSwipe];
!
!
!
- (void)upButtonTapped {
[self.model performMoveInDirection:F3HMoveDirectionUp
completionBlock:^(BOOL changed) {
if (changed) [self followUp]; }];
}

44.
Selectors
UISwipeGestureRecognizer *upSwipe = [[UISwipeGestureRecognizer alloc]
initWithTarget:self action:@selector(upButtonTapped)];
!
upSwipe.numberOfTouchesRequired = 1;
upSwipe.direction = UISwipeGestureRecognizerDirectionUp;
[self.view addGestureRecognizer:upSwipe];
!
!
!
- (void)upButtonTapped {
[self.model performMoveInDirection:F3HMoveDirectionUp
completionBlock:^(BOOL changed) {
if (changed) [self followUp]; }];
}

45.
Selectors
UISwipeGestureRecognizer *upSwipe = [[UISwipeGestureRecognizer alloc]
initWithTarget:self action:@selector(upButtonTapped)];
!
upSwipe.numberOfTouchesRequired = 1;
upSwipe.direction = UISwipeGestureRecognizerDirectionUp;
[self.view addGestureRecognizer:upSwipe];
!
!
!
- (void)upButtonTapped {
[self.model performMoveInDirection:F3HMoveDirectionUp
completionBlock:^(BOOL changed) {
if (changed) [self followUp]; }];
}

46.
Selectors
UISwipeGestureRecognizer *upSwipe = [[UISwipeGestureRecognizer alloc]
initWithTarget:self action:@selector(upButtonTapped)];
!
upSwipe.numberOfTouchesRequired = 1;
upSwipe.direction = UISwipeGestureRecognizerDirectionUp;
[self.view addGestureRecognizer:upSwipe];
!
!
!
- (void)upButtonTapped {
[self.model performMoveInDirection:F3HMoveDirectionUp
completionBlock:^(BOOL changed) {
if (changed) [self followUp]; }];
}

47.
Selectors in Swift
let upSwipe = UISwipeGestureRecognizer(target: self, action: Selector("up:"))
upSwipe.numberOfTouchesRequired = 1
upSwipe.direction = UISwipeGestureRecognizerDirection.Up
view.addGestureRecognizer(upSwipe)
@objc(up:)
func upCommand(r: UIGestureRecognizer!) {
assert(model != nil)
let m = model!
m.queueMove(MoveDirection.Up,
completion: { (changed: Bool) -> () in
if changed {
self.followUp()
}
})
}

48.
Selectors in Swift
let upSwipe = UISwipeGestureRecognizer(target: self, action: Selector("up:"))
upSwipe.numberOfTouchesRequired = 1
upSwipe.direction = UISwipeGestureRecognizerDirection.Up
view.addGestureRecognizer(upSwipe)
@objc(up:)
func upCommand(r: UIGestureRecognizer!) {
assert(model != nil)
let m = model!
m.queueMove(MoveDirection.Up,
completion: { (changed: Bool) -> () in
if changed {
self.followUp()
}
})
}

49.
Selectors in Swift
let upSwipe = UISwipeGestureRecognizer(target: self, action: Selector("up:"))
upSwipe.numberOfTouchesRequired = 1
upSwipe.direction = UISwipeGestureRecognizerDirection.Up
view.addGestureRecognizer(upSwipe)
@objc(up:)
func upCommand(r: UIGestureRecognizer!) {
assert(model != nil)
let m = model!
m.queueMove(MoveDirection.Up,
completion: { (changed: Bool) -> () in
if changed {
self.followUp()
}
})
}

50.
Questions?