Initial Commit

Shared/Assets.xcassets/AccentColor.colorset/Contents.json

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+{
+  "colors" : [
+    {
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

Shared/Assets.xcassets/AppIcon.appiconset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "iphone",
+      "scale" : "2x",
+      "size" : "20x20"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "3x",
+      "size" : "20x20"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "2x",
+      "size" : "29x29"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "3x",
+      "size" : "29x29"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "2x",
+      "size" : "40x40"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "3x",
+      "size" : "40x40"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "2x",
+      "size" : "60x60"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "3x",
+      "size" : "60x60"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "1x",
+      "size" : "20x20"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "20x20"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "1x",
+      "size" : "29x29"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "29x29"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "1x",
+      "size" : "40x40"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "40x40"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "1x",
+      "size" : "76x76"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "76x76"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "83.5x83.5"
+    },
+    {
+      "idiom" : "ios-marketing",
+      "scale" : "1x",
+      "size" : "1024x1024"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "16x16"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "16x16"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "32x32"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "32x32"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "128x128"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "128x128"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "256x256"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "256x256"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "512x512"
+    },
+    {
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "512x512"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

Shared/Assets.xcassets/Contents.json

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+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

Shared/ContentView.swift

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+import SwiftUI
+
+struct ContentView : View {
+    @State private var game = TicTacToe()
+
+    /// The number of wins of each player.
+    @State private var score = (x: 0, o: 0)
+
+    /// True iff no player has played yet.
+    @State private var isFirstTurn = true
+
+    var body: some View {
+        ZStack {
+            Color.black.edgesIgnoringSafeArea(.all)
+
+            VStack {
+                HStack {
+                    Spacer()
+                    VStack {
+                        Text("X")
+                            .foregroundColor(.teal)
+
+                        Text(String(score.x))
+                    }
+                    Spacer()
+
+                    Text(displayedMessage)
+
+                    Spacer()
+                    VStack {
+                        Text("O")
+                            .foregroundColor(.yellow)
+
+                        Text(String(score.o))
+                    }
+                    Spacer()
+                }
+
+                GeometryReader { bounds in
+                    grid3x3(size: 0.85 * min(bounds.size.width, bounds.size.height))
+                        .frame(width: bounds.size.width,
+                               height: bounds.size.height)
+                }
+
+                VStack {
+                    Button(isFirstTurn ? "RESET" : "NEW GAME") {
+                        withAnimation {
+                            if isFirstTurn {
+                                score = (0, 0)
+                            } else {
+                                game.reset()
+                                isFirstTurn = true
+                            }
+                        }
+                    }
+                    .foregroundColor(.red)
+                    .buttonStyle(PlainButtonStyle())
+
+                }
+            }
+            .font(.title.bold())
+            .foregroundColor(.white)
+            .padding()
+            .frame(minWidth: 300, minHeight: 400)
+        }
+    }
+
+    /// The message displayed to the player.
+    private var displayedMessage: String {
+        game.hasEnded ?
+        game.playerHasWon ? "You win!" : "Draw" :
+        "Player \(game.player.description)"
+    }
+
+    /// Returns a centered, evenly-spaced 3x3 grid of buttons.
+    private func grid3x3(size: CGFloat) -> some View {
+        ZStack {
+            Color.white
+                .frame(width: size, height: size)
+
+            VStack(spacing: 0.025 * size) {
+                ForEach(0..<3) { row in
+                    HStack(spacing: 0.025 * size) {
+                        ForEach(0..<3) { column in
+                            button(row, column, size: 0.95 * size / 3)
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    /// Returns a button having the given size,
+    /// positioned at the given row and column.
+    private func button(_ row: Int, _ column: Int, size: CGFloat) -> some View {
+        Button {
+            withAnimation {
+                game.playAt(row, column)
+                isFirstTurn = false
+                if game.playerHasWon {
+                    switch game.player {
+                    case .x:
+                        score.x += 1
+                    case .o:
+                        score.o += 1
+                    }
+                }
+            }
+        } label: {
+            Text(game[row, column]?.description ?? "")
+                .frame(width: size, height: size)
+        }
+        .font(.system(size: size / 2))
+        .foregroundColor(game.isMatchingAt(row, column) ? .green :
+                         game[row, column] == .x ? .teal : .yellow)
+        .background(.black)
+        .buttonStyle(BorderlessButtonStyle())
+        .disabled(game.hasEnded || game[row, column] != nil)
+    }
+}
+
+struct ContentView_Previews : PreviewProvider {
+    static var previews: some View {
+        ContentView()
+    }
+}

Shared/TicTacToe.swift

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+struct TicTacToe {
+    /// A tic-tac-toe player.
+    enum Player : CustomStringConvertible {
+        case x, o
+
+        var description: String {
+            switch self {
+            case .x:
+                return "X"
+            case .o:
+                return "O"
+            }
+        }
+    }
+
+    /// An array of 9 players, initially set to `nil`.
+    ///
+    /// `nil` descibes an empty position.
+    private var grid: [Player?] = Array(repeating: nil,
+                                         count: 9)
+
+    /// The indices of the matching elements in the grid.
+    private var matchingIndices: Set<Int> = []
+
+    /// The numbers of turns that passed.
+    private var turns: Int = 0
+
+    /// The current-turn player.
+    private(set) var player: Player = .x
+
+    /// True iff the current player has won.
+    var playerHasWon: Bool {
+        !matchingIndices.isEmpty
+    }
+
+    /// True iff this game has ended.
+    var hasEnded: Bool {
+        playerHasWon || turns == 9
+    }
+
+    /// Returns the player at the given row and column.
+    subscript(row: Int, column: Int) -> Player? {
+        grid[3 * row + column]
+    }
+
+    /// Returns true if the player won by matching
+    /// the given row and column.
+    func isMatchingAt(_ row: Int, _ column: Int) -> Bool {
+        matchingIndices.contains(3 * row + column)
+    }
+
+    /// Determines the winner by matching the values
+    /// at the given indices.
+    private mutating func match(_ i: Int, _ j: Int, _ k: Int) {
+        if grid[i] == grid[j] && grid[j] == grid[k] {
+            for index in [i, j, k] {
+                matchingIndices.insert(index)
+            }
+        }
+    }
+
+    /// Plays this game at the given row and column.
+    mutating func playAt(_ row: Int, _ column: Int) {
+        let index = 3 * row + column
+        grid[index] = player
+        // Try to match along all possible directions.
+        //
+        //    0   1   2
+        // 0 [0] [1] [2]
+        // 1 [3] [4] [5]
+        // 2 [6] [7] [8]
+        //
+        // Match along the given row.
+        match(3 * row, 3 * row + 1, 3 * row + 2)
+        // Match along the given column.
+        match(column, column + 3, column + 6)
+        // If we are on the diagnonal (0, 4, 8):
+        if row == column {
+            match(0, 4, 8)
+        }
+        // If we are on the diagnonal (2, 4, 6):
+        if row + column == 2 {
+            match(2, 4, 6)
+        }
+        turns += 1
+        if !playerHasWon {
+            player = (player == .x) ? .o : .x
+        }
+    }
+
+    /// Starts a new game with the same starting player
+    /// as the current one.
+    mutating func reset() {
+        for index in grid.indices {
+            grid[index] = nil
+        }
+        matchingIndices.removeAll()
+        turns = 0
+    }
+}