C++------虚析构函数与纯虚析构函数

#include 
#include 

using namespace std;

//虚析构与纯虚析构

class Animal
{
public:
	virtual void speak()
	{
		cout << "动物在说话" << endl;
	}
	~Animal()
	{
		cout << "Animal的析构调用" << endl;
	}
};
class Cat :public Animal
{
public:
	Cat(const char* name)
	{
		this->m_Name = new char[strlen(name) + 1];
		strcpy_s(this->m_Name, strlen(name) + 1, name);
	}
	void speak()
	{
		cout << "小猫也在说话" << endl;
	}
	~Cat()
	{
		if (this->m_Name != NULL) {
			delete[] this->m_Name;
			this->m_Name = NULL;
		}
		cout << "小猫的析构函数" << endl;
	}
	char * m_Name;
};

void test01()
{
	Animal *cat1 = new Cat("Tom");
	cat1->speak();

	delete cat1;
	//此时调用的是Animal的析构,没有调用Cat的析构;
}
class Animal2
{
public:
	virtual void speak()
	{
		cout << "动物在说话" << endl;
	}
	//普通析构,是不会调用子类析构的,所以可能导致释放的不干净;
	//所以采用虚析构;
	virtual ~Animal2()
	{
		cout << "Animal2的析构调用" << endl;
	}
};
class Cat2 :public Animal2
{
public:
	Cat2(const char* name)
	{
		this->m_Name = new char[strlen(name) + 1];
		strcpy_s(this->m_Name, strlen(name) + 1, name);
	}
	void speak()
	{
		cout << "小猫也在说话" << endl;
	}
	~Cat2()
	{
		if (this->m_Name != NULL) {
			delete[] this->m_Name;
			this->m_Name = NULL;
		}
		cout << "小猫的析构函数" << endl;
	}
	char * m_Name;
};

void test02()
{
	Animal2 *cat2 = new Cat2("Tom");
	cat2->speak();

	delete cat2;
	//此时先Cat2的析构,然后再是Animal2的析构;
	//本来就可肯定应该调用Animal2的析构的;
}

class Animal3
{
public:
	virtual void speak()
	{
		cout << "动物在说话" << endl;
	}
	//普通析构,是不会调用子类析构的,所以可能导致释放的不干净;
	//所以采用虚析构;
	//若采用纯虚析构;
	//外部无法解析,因为纯虚析构没有实现,所以编译器无法通过;
	//只能类内声明,类外实现;
	//如果出现了纯虚析构函数,也算是抽象类了。
	virtual ~Animal3() = 0;
};
Animal3::~Animal3()
{
	cout << "Animal3的纯虚析构" << endl;
}
class Cat3 :public Animal3
{
public:
	Cat3(const char* name)
	{
		this->m_Name = new char[strlen(name) + 1];
		strcpy_s(this->m_Name, strlen(name) + 1, name);
	}
	void speak()
	{
		cout << "小猫也在说话" << endl;
	}
	~Cat3()
	{
		if (this->m_Name != NULL) {
			delete[] this->m_Name;
			this->m_Name = NULL;
		}
		cout << "小猫的析构函数" << endl;
	}
	char * m_Name;
};
void test03()
{
	Animal3 *cat3 = new Cat3("Tom");
	cat3->speak();

	delete cat3;

}

int main()
{
	test01();
	test02();
	test03();
	return 0;
}

 

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