C++ 补充 & C++ 11 - C++ dynamic_cast用法详解

dynamic_cast

动态类型转换

将一个基类对象指针cast到继承类指针，dynamic_cast 会根据基类指针是否真正指向继承类指针来做相应处理。失败返回null，成功返回正常cast后的对象指针；

将一个基类对象引用cast 继承类对象，dynamic_cast 会根据基类对象是否真正属于继承类来做相应处理。失败抛出异常bad_cast
注意：dynamic_cast在将父类cast到子类时，父类必须要有虚函数一起玩。

demo 代码(一)

#include <iostream>

using namespace std;

class Animal
{
public:
	virtual void cry() = 0;

};

class Cat : public Animal
{
public:
	void cry()
	{
		cout << "喵喵" << endl;
	}

	void play()
	{
		cout << "爬树" << endl;
	}
};

class Dog :public Animal
{
public:
	void cry()
	{
		cout << "旺旺" << endl;
	}

	void play()
	{
		cout << "溜达溜达" << endl;
	}
};

void animalPlay(Animal* animal)
{
	animal->cry();

	Dog* pDog = dynamic_cast<Dog*>(animal);
	if (pDog)
	{
		pDog->play();
	}
	else /* pDog == NULL */
	{
		cout << "不是狗, 别骗我!" << endl;
	}

	Cat* pCat = dynamic_cast<Cat*>(animal);
	if (pCat)
	{
		pCat->play();
	}
	else /* pDog == NULL */
	{
		cout << "不是猫, 别骗我!" << endl;
	}

}

int main(void)
{
	Dog* dog1 = new Dog();
	Animal* a1 = dog1;

	//animalPlay(a1);
	
	Dog dog2;
	animalPlay(dog2);

	Cat* cat1 = new Cat();
	Animal* a2 = cat1;

	//animalPlay(a2);
	Cat cat2;
	animalPlay(cat2);

	system("pause");
	return 0;
}

结语:

时间: 2020-07-02