C++のアクセス指定子と多重継承の基本と応用解説

#include <iostream>
using namespace std;

class PublicExample {
public:
    int publicVar;

    void display() {
        cout << "Public Variable: " << publicVar << endl;
    }
};

int main() {
    PublicExample obj;
    obj.publicVar = 5; // クラス外部からアクセス可能
    obj.display();
    return 0;
}

#include <iostream>
using namespace std;

class Base {
protected:
    int protectedVar;

public:
    void setVar(int val) {
        protectedVar = val;
    }
};

class Derived : public Base {
public:
    void display() {
        cout << "Protected Variable: " << protectedVar << endl;
    }
};

int main() {
    Derived obj;
    obj.setVar(10); // クラス外部からはsetVar経由でアクセス
    obj.display();
    return 0;
}

#include <iostream>
using namespace std;

class PrivateExample {
private:
    int privateVar;

public:
    void setVar(int val) {
        privateVar = val;
    }

    void display() {
        cout << "Private Variable: " << privateVar << endl;
    }
};

int main() {
    PrivateExample obj;
    obj.setVar(15); // クラス外部からはsetVar経由でアクセス
    obj.display();
    return 0;
}

#include <iostream>
using namespace std;

class ClassA {
public:
    void methodA() {
        cout << "Method from ClassA" << endl;
    }
};

class ClassB {
public:
    void methodB() {
        cout << "Method from ClassB" << endl;
    }
};

class DerivedClass : public ClassA, public ClassB {
public:
    void methodDerived() {
        cout << "Method from DerivedClass" << endl;
    }
};

int main() {
    DerivedClass obj;
    obj.methodA();       // ClassAのメソッドを呼び出し
    obj.methodB();       // ClassBのメソッドを呼び出し
    obj.methodDerived(); // DerivedClassのメソッドを呼び出し
    return 0;
}

#include <iostream>
using namespace std;

class Base1 {
public:
    Base1() {
        cout << "Base1 constructor" << endl;
    }
};

class Base2 {
public:
    Base2() {
        cout << "Base2 constructor" << endl;
    }
};

class Derived : public Base1, public Base2 {
public:
    Derived() {
        cout << "Derived constructor" << endl;
    }
};

int main() {
    Derived obj;
    return 0;
}

#include <iostream>
using namespace std;

class Base1 {
protected:
    int protectedVar;
public:
    Base1() : protectedVar(0) {}
};

class Base2 {
private:
    int privateVar;
public:
    Base2() : privateVar(0) {}
    void setPrivateVar(int val) {
        privateVar = val;
    }
    int getPrivateVar() const {
        return privateVar;
    }
};

class Derived : public Base1, public Base2 {
public:
    void setProtectedVar(int val) {
        protectedVar = val; // Base1から継承されたprotectedメンバーにアクセス可能
    }
    void display() {
        cout << "Protected Variable: " << protectedVar << endl;
        cout << "Private Variable: " << getPrivateVar() << endl; // Base2のpublicメソッドを経由してアクセス
    }
};

int main() {
    Derived obj;
    obj.setProtectedVar(10);
    obj.setPrivateVar(20);
    obj.display();
    return 0;
}

#include <iostream>
using namespace std;

class Base {
public:
    void show() {
        cout << "Base class" << endl;
    }
};

class Derived1 : public Base {
};

class Derived2 : public Base {
};

class DerivedFinal : public Derived1, public Derived2 {
};

int main() {
    DerivedFinal obj;
    // obj.show(); // エラー：showメソッドがあいまい
    return 0;
}

#include <iostream>
using namespace std;

class Base {
public:
    void show() {
        cout << "Base class" << endl;
    }
};

class Derived1 : virtual public Base {
};

class Derived2 : virtual public Base {
};

class DerivedFinal : public Derived1, public Derived2 {
};

int main() {
    DerivedFinal obj;
    obj.show(); // 正常に動作
    return 0;
}

#include <iostream>
using namespace std;

// 各インターフェースの定義
class Printer {
public:
    virtual void print() = 0;
};

class Scanner {
public:
    virtual void scan() = 0;
};

// 多重継承による統合クラス
class MultiFunctionDevice : public Printer, public Scanner {
public:
    void print() override {
        cout << "Printing document..." << endl;
    }

    void scan() override {
        cout << "Scanning document..." << endl;
    }
};

int main() {
    MultiFunctionDevice device;
    device.print();
    device.scan();
    return 0;
}

#include <iostream>
using namespace std;

// ミックスインクラスの定義
class Logging {
public:
    void log(const string& message) {
        cout << "Log: " << message << endl;
    }
};

class ErrorHandling {
public:
    void handleError(const string& error) {
        cout << "Error: " << error << endl;
    }
};

// 基本クラス
class Application {
public:
    void run() {
        cout << "Running application..." << endl;
    }
};

// ミックスインクラスを統合したクラス
class AdvancedApplication : public Application, public Logging, public ErrorHandling {
};

int main() {
    AdvancedApplication app;
    app.run();
    app.log("Application started");
    app.handleError("No errors");
    return 0;
}

#include <iostream>
using namespace std;

class Sample {
public:
    int publicVar;
protected:
    int protectedVar;
private:
    int privateVar;

public:
    void setValues(int pub, int prot, int priv) {
        publicVar = pub;
        protectedVar = prot;
        privateVar = priv;
    }

    void display() {
        cout << "Public Variable: " << publicVar << endl;
        cout << "Protected Variable: " << protectedVar << endl;
        cout << "Private Variable: " << privateVar << endl;
    }
};

int main() {
    Sample obj;
    obj.setValues(1, 2, 3);
    obj.publicVar = 10; // 直接アクセス可能
    // obj.protectedVar = 20; // エラー: protectedメンバーには直接アクセス不可
    // obj.privateVar = 30; // エラー: privateメンバーには直接アクセス不可
    obj.display();
    return 0;
}

#include <iostream>
using namespace std;

class Animal {
public:
    virtual void makeSound() {
        cout << "Some generic animal sound" << endl;
    }
};

class WingedAnimal {
public:
    virtual void fly() {
        cout << "Flapping wings" << endl;
    }
};

class Bat : public Animal, public WingedAnimal {
public:
    void makeSound() override {
        cout << "Screech" << endl;
    }
    void fly() override {
        cout << "Bat is flying" << endl;
    }
};

int main() {
    Bat bat;
    bat.makeSound();
    bat.fly();
    return 0;
}