一文带你学习C++中的派生机制

class Base {
public:
    int public_var;
protected:
    int protected_var;
private:
    int private_var;
};

class Derived : public Base {
public:
    void setVar(int a, int b, int c)
    {
        public_var = a;  //公有成员可以在派生类中访问
        protected_var = b;  //受保护成员可以在派生类中访问
        // private_var = c;  //私有成员无法在派生类中访问
    }
};

class Base {
public:
    int public_var;
protected:
    int protected_var;
private:
    int private_var;
};

class Derived : protected Base {
public:
    void setVar(int a, int b, int c)
    {
        public_var = a;  //公有成员可以在派生类中访问
        protected_var = b;  //受保护成员可以在派生类中访问
        // private_var = c;  //私有成员无法在派生类中访问
    }
};

class Base {
public:
    int public_var;
protected:
    int protected_var;
private:
    int private_var;
};

class Derived : private Base {
public:
    void setVar(int a, int b, int c)
    {
        public_var = a;  //公有成员可以在派生类中访问
        protected_var = b;  //受保护成员可以在派生类中访问
        // private_var = c;  //私有成员无法在派生类中访问
    }
};

class Derived_class : access_specifier Base_class {
    // 包含新成员和覆盖的函数等
};

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

class Derived : public Base {
public:
    void print() {
        std::cout << "Derived" << std::endl;
    }
};

int main()
{
    Base b;
    Derived d;

    b.print(); //输出 Base
    d.print(); //输出 Derived

    return 0;
}

class Derived : access_specifier Base1, access_specifier Base2, ... {
    // 包含新成员和覆盖的函数等
};

class Base1 {
public:
    void print1() {
        std::cout << "Base1" << std::endl;
    }
};

class Base2 {
public:
    void print2() {
        std::cout << "Base2" << std::endl;
    }
};

class Derived : public Base1, protected Base2 {
public:
    void print() {
        print1();
        //print2(); //private 成员不能在派生类之外的成员函数中访问
    }
};

int main()
{
    Derived d;
    d.print();

    return 0;
}

class Root {
public:
    int i;
};

class A : public virtual Root {
public:
    int j;
};

class B : public virtual Root {
public:
    int k;
};

class C : public A, public B {
public:
    void sum() {
        i = j + k;
    }
};

int main()
{
    C c;

    c.j = 10;
    c.k = 20;
    c.sum();

    std::cout << "Sum of j and k is " << c.i << std::endl;

    return 0;
}

class Base {
public:
    int publicVar;
protected:
    int protectedVar;
private:
    int privateVar;
public:
    void print() {
        std::cout << "publicVar: " << publicVar << std::endl;
        std::cout << "protectedVar: " << protectedVar << std::endl;
        std::cout << "privateVar: " << privateVar << std::endl;
    }
};

class Derived : public Base {
public:
    int additionalVar;
public:
    void printAdditionalVar() {
        std::cout << "additionalVar: " << additionalVar << std::endl;
    }
};

int main()
{
    Derived derived;
    derived.publicVar = 1;
    //derived.protectedVar = 2;  //protected 成员不能直接在类外部访问
    derived.print();  //基类中的公有成员和受保护成员可以在派生类对象中访问
    derived.additionalVar = 3;
    derived.printAdditionalVar();  //派生类中的成员可以直接访问
    Base& base = derived;  //派生类的对象可以赋值给基类对象
    base.print();  //基类中的成员可以在基类对象中访问
    return 0;
}