React のチュートリアル（９）

※ これは 2023/05/18 時点の create-react-app@5.0.1 の情報です

最新版では動作が異なる可能性がありますのでご注意ください

前回に引き続き React のチュートリアルの続きを焦らず少しずつ進める

前回勝敗を表示するようにしたら、次は巻き戻しできるようにするらしい

前回の index.js の下記、Board と Game に

class Board extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      squares: Array(9).fill(null),
      xIsNext: true,
    };
  }

  handleClick(i) {
    const squares = this.state.squares.slice();
    if (calculateWinner(squares) || squares[i]) {
      return;
    }
    squares[i] = this.state.xIsNext ? 'X' : 'O';
    this.setState({
      squares: squares,
      xIsNext: !this.state.xIsNext,
    });
  }

  renderSquare(i) {
    return (
      <Square
        value={this.state.squares[i]}         // <--
        onClick={() => this.handleClick(i)}   // <--
      />
    );
  }

  render() {
    const winner = calculateWinner(this.state.squares);              // <--
    let status;                                                      // <--
    if (winner) {                                                    // <--
      status = 'Winner: ' + winner;                                  // <--
    } else {                                                         // <--
      status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');   // <--
    }                                                                // <--

    return (
      <div>
        <div className="status">{status}</div>
        <div className="board-row">
          {this.renderSquare(0)}
          {this.renderSquare(1)}
          {this.renderSquare(2)}
        </div>
        <div className="board-row">
          {this.renderSquare(3)}
          {this.renderSquare(4)}
          {this.renderSquare(5)}
        </div>
        <div className="board-row">
          {this.renderSquare(6)}
          {this.renderSquare(7)}
          {this.renderSquare(8)}
        </div>
      </div>
    );
  }
}

class Game extends React.Component {
  render() {
    return (
      <div className="game">
        <div className="game-board">
          <Board />
        </div>
        <div className="game-info">
          <div>{/* status */}</div>
          <ol>{/* TODO */}</ol>
        </div>
      </div>
    );
  }
}

履歴情報を管理し、結果表示を Board から Game に移動する下記のようなコードに変更

class Board extends React.Component {
  handleClick(i) {
    const squares = this.state.squares.slice();
    if (calculateWinner(squares) || squares[i]) {
      return;
    }
    squares[i] = this.state.xIsNext ? 'X' : 'O';
    this.setState({
      squares: squares,
      xIsNext: !this.state.xIsNext,
    });
  }

  renderSquare(i) {
    return (
      <Square
        value={this.props.squares[i]}           // <--
        onClick={() => this.props.onClick(i)}   // <--
      />
    );
  }

  render() {
    return (
      <div>
        <div className="board-row">
          {this.renderSquare(0)}
          {this.renderSquare(1)}
          {this.renderSquare(2)}
        </div>
        <div className="board-row">
          {this.renderSquare(3)}
          {this.renderSquare(4)}
          {this.renderSquare(5)}
        </div>
        <div className="board-row">
          {this.renderSquare(6)}
          {this.renderSquare(7)}
          {this.renderSquare(8)}
        </div>
      </div>
    );
  }
}

class Game extends React.Component {
  constructor(props) {                // <--
    super(props);                     // <--
    this.state = {                    // <--
      history: [{                     // <--
        squares: Array(9).fill(null), // <--
      }],                             // <--
      xIsNext: true,                  // <--
    };                                // <--
  }                                   // <--

  render() {
    const history = this.state.history;                             // <--
    const current = history[history.length - 1];                    // <--
    const winner = calculateWinner(current.squares);                // <--
    let status;                                                     // <--
    if (winner) {                                                   // <--
      status = 'Winner: ' + winner;                                 // <--
    } else {                                                        // <--
      status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');  // <--
    }                                                               // <--

    return (
      <div className="game">
        <div className="game-board">
          <Board />
        </div>
        <div className="game-info">
          <div>{/* status */}</div>
          <ol>{/* TODO */}</ol>
        </div>
      </div>
    );
  }
}

次に Board にあった handleClick 関数に下記のように改変して Game に移動

class Game extends React.Component {
  constructor(props) { 
    super(props);
    this.state = {
      history: [{
        squares: Array(9).fill(null),
      }],
      xIsNext: true,
    };
  }

  handleClick(i) {                                 // <--
    const history = this.state.history;            // <--
    const current = history[history.length - 1];   // <--
    const squares = current.squares.slice();       // <--
    if (calculateWinner(squares) || squares[i]) {  // <--
      return;                                      // <--
    }                                              // <--
    squares[i] = this.state.xIsNext ? 'X' : 'O';   // <--
    this.setState({                                // <--
      history: history.concat([{                   // <--
        squares: squares,                          // <--
      }]),                                         // <--
      xIsNext: !this.state.xIsNext,                // <--
    });                                            // <--
  }                                                // <--

  render() {
    const history = this.state.history;
    const current = history[history.length - 1];
    const winner = calculateWinner(current.squares);
    let status;
    if (winner) {
      status = 'Winner: ' + winner;
    } else {
      status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
    }

    return (
      <div className="game">
        <div className="game-board">
    return (
      <div className="game">
        <div className="game-board">
          <Board
            squares={current.squares}              // <--
            onClick={(i) => this.handleClick(i)}   // <--
          />                                       
        </div>
        <div className="game-info">
          <div>{status}</div>                      // <--
          <ol>{/* TODO */}</ol>
        </div>
      </div>
    );

Game にいろいろ移してきたこの時点で全体のコードはこんな感じ

import React from 'react';
import ReactDOM from 'react-dom/client';
import './index.css';

function Square(props) {
  return (
    <button className="square" onClick={props.onClick}>
      {props.value}
    </button>
  );
}

class Board extends React.Component {
  renderSquare(i) {
    return (
      <Square
        value={this.props.squares[i]}
        onClick={() => this.props.onClick(i)}
      />
    );
  }

  render() {
    return (
      <div>
        <div className="board-row">
          {this.renderSquare(0)}
          {this.renderSquare(1)}
          {this.renderSquare(2)}
        </div>
        <div className="board-row">
          {this.renderSquare(3)}
          {this.renderSquare(4)}
          {this.renderSquare(5)}
        </div>
        <div className="board-row">
          {this.renderSquare(6)}
          {this.renderSquare(7)}
          {this.renderSquare(8)}
        </div>
      </div>
    );
  }
}

class Game extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      history: [{
        squares: Array(9).fill(null),
      }],
      xIsNext: true,
    };
  }

  handleClick(i) {
    const history = this.state.history;
    const current = history[history.length - 1];
    const squares = current.squares.slice();
    if (calculateWinner(squares) || squares[i]) {
      return;
    }
    squares[i] = this.state.xIsNext ? 'X' : 'O';
    this.setState({
      history: history.concat([{
        squares: squares,
      }]),
      xIsNext: !this.state.xIsNext,
    });
  }

  render() {
    const history = this.state.history;
    const current = history[history.length - 1];
    const winner = calculateWinner(current.squares);
    let status;
    if (winner) {
      status = 'Winner: ' + winner;
    } else {
      status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
    }

    return (
      <div className="game">
        <div className="game-board">
          <Board
            squares={current.squares}
            onClick={(i) => this.handleClick(i)}
          />
        </div>
        <div className="game-info">
          <div>{status}</div>
          <ol>{/* TODO */}</ol>
        </div>
      </div>
    );
  }
}

// ========================================

const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(<Game />);

function calculateWinner(squares) {
  const lines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6],
  ];
  for (let i = 0; i < lines.length; i++) {
    const [a, b, c] = lines[i];
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return squares[a];
    }
  }
  return null;
}

これを実行、VSCode のターミナルから下記コマンドを実行してブラウザで開く

npm start

履歴を持つように結構変えたけどリファクタリングで動作は変わらない