C/C++析构函数与虚函数

最新推荐文章于 2024-08-21 08:30:00 发布

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本文通过四个C++代码示例，展示了基类指针指向派生类对象时构造函数与析构函数的调用顺序，以及虚函数机制如何确保正确的函数调用。

a.第一段代码：

#include<iostream>
using namespace std;
class ClxBase{
public:
	ClxBase() {cout << "Output from the constructor of class ClxBase!" << endl;};
	 ~ClxBase() {cout << "Output from the destructor of class ClxBase!" << endl;};

        void DoSomething() { cout << "Do something in class ClxBase!" << endl; };
};

class ClxDerived : public ClxBase{
public:
	ClxDerived() {cout << "Output from the constructor of class ClxDerived!" << endl;};
	~ClxDerived() { cout << "Output from the destructor of class ClxDerived!" << endl; };

	void DoSomething() { cout << "Do something in class ClxDerived!" << endl; };
};
int main()
{ 
	ClxDerived *p =  new ClxDerived;
	p->DoSomething();
	delete p;

	return 0;
}

输出结果：

b.第二段代码：

#include<iostream>
using namespace std;
class ClxBase{
public:
	ClxBase() {cout << "Output from the constructor of class ClxBase!" << endl;};
	 ~ClxBase() {cout << "Output from the destructor of class ClxBase!" << endl;};

        void DoSomething() { cout << "Do something in class ClxBase!" << endl; };
};

class ClxDerived : public ClxBase{
public:
	ClxDerived() {cout << "Output from the constructor of class ClxDerived!" << endl;};
	~ClxDerived() { cout << "Output from the destructor of class ClxDerived!" << endl; };

	void DoSomething() { cout << "Do something in class ClxDerived!" << endl; };
};
int main()
{ 
	
<pre name="code" class="cpp" style="color: rgb(94, 94, 94); line-height: 21.666667938232422px; text-align: justify;">       ClxBase *p =  new ClxDerived;

p->DoSomething();delete p;return 0;}

运行结果：

C.第三段代码：

#include<iostream>
using namespace std;
class ClxBase{
public:
	ClxBase() {cout << "Output from the constructor of class ClxBase!" << endl;};
	virtual ~ClxBase() {cout << "Output from the destructor of class ClxBase!" << endl;};

	virtual void DoSomething() { cout << "Do something in class ClxBase!" << endl; };
};

class ClxDerived : public ClxBase{
public:
	ClxDerived() {cout << "Output from the constructor of class ClxDerived!" << endl;};
	 ~ClxDerived() { cout << "Output from the destructor of class ClxDerived!" << endl; };

	void DoSomething() { cout << "Do something in class ClxDerived!" << endl; };
};
int main()
{ 
	ClxDerived *p =  new ClxDerived;
	p->DoSomething();
	delete p;

	return 0;
}

输出结果：

d.第四段代码：

#include<iostream>
using namespace std;
class ClxBase{
public:
	ClxBase() {cout << "Output from the constructor of class ClxBase!" << endl;};
	virtual ~ClxBase() {cout << "Output from the destructor of class ClxBase!" << endl;};

	virtual void DoSomething() { cout << "Do something in class ClxBase!" << endl; };
};

class ClxDerived : public ClxBase{
public:
	ClxDerived() {cout << "Output from the constructor of class ClxDerived!" << endl;};
	 ~ClxDerived() { cout << "Output from the destructor of class ClxDerived!" << endl; };

	void DoSomething() { cout << "Do something in class ClxDerived!" << endl; };
};
int main()
{ 
	ClxBase *p =  new ClxDerived;
	p->DoSomething();
	delete p;

	return 0;
}

运行结果：