C++多继承 | ASD の小窝

C++多继承

语法

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class D: public A, private B, protected C{
    //类D新增加的成员
}

构造

子类构造会按照继承顺序默认调用父类的无参构造

显式调用父类的构造(列表初始化)，与书写顺序无关，初始化顺序依然由继承顺序决定

析构执行顺序与构造执行顺序相反

#include <iostream>
using namespace std;

// 基类
class BaseA
{
public:
    BaseA()
    {
        cout << "BaseA constructor" << endl;
    }
    BaseA(int a, int b);
    ~BaseA();

protected:
    int m_a;
    int m_b;
};
BaseA::BaseA(int a, int b) : m_a(a), m_b(b)
{
    cout << "BaseA constructor" << endl;
}
BaseA::~BaseA()
{
    cout << "BaseA destructor" << endl;
}

// 基类
class BaseB
{
public:
    BaseB()
    {
        cout << "BaseB constructor" << endl;
    }
    BaseB(int c, int d);
    ~BaseB();

protected:
    int m_c;
    int m_d;
};
BaseB::BaseB(int c, int d) : m_c(c), m_d(d)
{
    cout << "BaseB constructor" << endl;
}
BaseB::~BaseB()
{
    cout << "BaseB destructor" << endl;
}

// 派生类，构造执行顺序是A,B和子类
class Derived : public BaseA, public BaseB
{
public:
    Derived()
    {
        cout << "Derived constructor" << endl;
    }
    Derived(int a, int b, int c, int d, int e);
    ~Derived();

public:
    void show();

private:
    int m_e;
};

// 派生类构造函数,构造执行顺序依然是A,B和子类
Derived::Derived(int a, int b, int c, int d, int e) : BaseB(a, b), BaseA(c, d), m_e(e)
{
    cout << "Derived constructor" << endl;
}
Derived::~Derived()
{
    cout << "Derived destructor" << endl;
}
void Derived::show()
{
    cout << m_a << ", " << m_b << ", " << m_c << ", " << m_d << ", " << m_e << endl;
}

int main()
{
    Derived obj1;
    cout << "--------------------" << endl;
    Derived obj(1, 2, 3, 4, 5);
    obj.show();
    return 0;
}

对于相同的函数和属性，依旧使用::来控制访问