[C++] enumの使い方と基本的な活用例

#include <iostream>
// 曜日を表すenumの宣言
enum Day {
    Sunday,    // 0
    Monday,    // 1
    Tuesday,   // 2
    Wednesday, // 3
    Thursday,  // 4
    Friday,    // 5
    Saturday   // 6
};
int main() {
    Day today = Wednesday;
    std::cout << "Today is " << today << std::endl;
    return 0;
}

#include <iostream>
void printDay() {
    enum Day { Sunday, Monday, Tuesday };
    Day today = Monday;
    std::cout << "Today is " << today << std::endl;
}
int main() {
    printDay();
    // Day today = Sunday; // エラー: 'Day'はprintDay関数内でのみ有効
    return 0;
}

#include <iostream>
// 型指定されたenum classの宣言
enum class Color : int {
    Red,    // 0
    Green,  // 1
    Blue    // 2
};
int main() {
    Color myColor = Color::Green;
    // std::cout << myColor; // エラー: 型安全のため直接出力できない
    return 0;
}

#include <iostream>
// 明示的に値を指定したenumの宣言
enum Month {
    January = 1,
    February,
    March,
    April,
    May,
    June,
    July,
    August,
    September,
    October,
    November,
    December
};
int main() {
    Month currentMonth = March;
    std::cout << "Current month is " << currentMonth << std::endl;
    return 0;
}

#include <iostream>
// キャラクターの状態を表すenum
enum CharacterState {
    Idle,    // 待機中
    Walking, // 歩行中
    Running, // 走行中
    Jumping  // ジャンプ中
};
int main() {
    CharacterState currentState = Walking;
    if (currentState == Walking) {
        std::cout << "The character is walking." << std::endl;
    }
    return 0;
}

#include <iostream>
// フラグを表すenum
enum FilePermission {
    Read    = 1 << 0, // 0001
    Write   = 1 << 1, // 0010
    Execute = 1 << 2  // 0100
};
int main() {
    int myPermissions = Read | Write; // 読み取りと書き込みの権限を設定
    if (myPermissions & Read) {
        std::cout << "Read permission is granted." << std::endl;
    }
    return 0;
}

#include <iostream>
// 操作を表すenum
enum Operation {
    Add,
    Subtract,
    Multiply,
    Divide
};
int main() {
    Operation op = Multiply;
    int a = 10, b = 5;
    int result = 0;
    switch (op) {
        case Add:
            result = a + b;
            break;
        case Subtract:
            result = a - b;
            break;
        case Multiply:
            result = a * b;
            break;
        case Divide:
            result = a / b;
            break;
        default:
            std::cout << "Invalid operation." << std::endl;
            return 1;
    }
    std::cout << "Result: " << result << std::endl;
    return 0;
}

#include <iostream>
// 色を表すenum class
enum class Color {
    Red,
    Green,
    Blue
};
// 方向を表すenum class
enum class Direction {
    North,
    South,
    East,
    West
};
int main() {
    Color myColor = Color::Green;
    Direction myDirection = Direction::North;
    // 型安全のため、異なるenum classの比較はできない
    // if (myColor == myDirection) { } // エラー
    // enum classの値を整数にキャスト
    int colorValue = static_cast<int>(myColor);
    std::cout << "Color value: " << colorValue << std::endl;
    return 0;
}

#include <iostream>
// フラグを表すenum
enum Option {
    None    = 0,      // 0000
    Bold    = 1 << 0, // 0001
    Italic  = 1 << 1, // 0010
    Underline = 1 << 2 // 0100
};
int main() {
    int textStyle = Bold | Italic; // 太字とイタリックを設定
    // フラグのチェック
    if (textStyle & Bold) {
        std::cout << "Bold is set." << std::endl;
    }
    // フラグの解除
    textStyle &= ~Italic;
    if (!(textStyle & Italic)) {
        std::cout << "Italic is not set." << std::endl;
    }
    return 0;
}

#include <iostream>
// エラーコードを表すenum
enum ErrorCode {
    Success,
    NotFound,
    PermissionDenied,
    UnknownError
};
ErrorCode performOperation() {
    // 何らかの操作を行う
    return NotFound; // エラーを返す
}
int main() {
    ErrorCode result = performOperation();
    switch (result) {
        case Success:
            std::cout << "Operation succeeded." << std::endl;
            break;
        case NotFound:
            std::cout << "Error: Not found." << std::endl;
            break;
        case PermissionDenied:
            std::cout << "Error: Permission denied." << std::endl;
            break;
        case UnknownError:
            std::cout << "Error: Unknown error." << std::endl;
            break;
    }
    return 0;
}

#include <iostream>
// 設定項目を表すenum
enum Setting {
    Volume,
    Brightness,
    Contrast
};
void adjustSetting(Setting setting, int value) {
    switch (setting) {
        case Volume:
            std::cout << "Adjusting volume to " << value << std::endl;
            break;
        case Brightness:
            std::cout << "Adjusting brightness to " << value << std::endl;
            break;
        case Contrast:
            std::cout << "Adjusting contrast to " << value << std::endl;
            break;
    }
}
int main() {
    adjustSetting(Volume, 10);
    adjustSetting(Brightness, 5);
    return 0;
}

enum class TrafficLight {
    TrafficLight_Red,
    TrafficLight_Yellow,
    TrafficLight_Green
};

enum class ErrorCode {
    Success,        // 操作が成功した
    NotFound,       // リソースが見つからない
    PermissionDenied, // 権限がない
    UnknownError    // 不明なエラー
};

// ドキュメント化されたenum
/**
 * @brief アプリケーションの状態を表す列挙型
 */
enum class AppState {
    Initializing,  // 初期化中
    Running,       // 実行中
    Paused,        // 一時停止中
    Terminated     // 終了
};