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c++中dynamic_pointer_cast强制类型转换

程序员文章站 2022-07-12 22:57:59
...
#include <iostream>
#include <memory>

using namespace std;

class CBase
{
public:
	CBase() { }
	virtual ~CBase() { }

	void myBase()
	{
		cout << "CBase::myBase" << endl;
	}
};

class CDerive : public CBase
{
public:
	CDerive() { }
	~CDerive() { }

	void myDerive()
	{
		cout << "CDerive::myDerive" << endl;
	}
};

int main(void)
{
	//上行的转换(派生类到基类的转换)
	shared_ptr<CDerive> spDeriveUp;
	shared_ptr<CBase> spBaseUp;
	spDeriveUp = make_shared<CDerive>();
	spBaseUp = dynamic_pointer_cast<CBase>(spDeriveUp);
	spBaseUp->myBase();

	//下行的转换(基类到派生类的转换)
	shared_ptr<CDerive> spDeriveDown;
	shared_ptr<CBase> spBaseDown;
	spBaseDown = make_shared<CBase>();
	spDeriveDown = dynamic_pointer_cast<CDerive>(spBaseDown);
	if (spDeriveDown == NULL)	//由于会进行类型的检查,这边是返回NULL
		cout << "spDeriveDown is null" << endl;

	/*
	shared_ptr<CDerive> spDeriveDown;
	shared_ptr<CBase> spBaseDown;
	spBaseDown = make_shared<CDerive>();
	spDeriveDown = dynamic_pointer_cast<CDerive>(spBaseDown);
	if (spDeriveDown == NULL)	//由于会进行类型的检查,这边是返回NULL
		cout << "spDeriveDown is null" << endl;
	spDeriveDown->myDerive();
	*/

	return 0;
}

运行结果:

c++中dynamic_pointer_cast强制类型转换

#include <iostream>
#include <memory>

using namespace std;

class CBase
{
public:
	CBase() { }
	virtual ~CBase() { }

	void myBase()
	{
		cout << "CBase::myBase" << endl;
	}
};

class CDerive : public CBase
{
public:
	CDerive() { }
	~CDerive() { }

	void myDerive()
	{
		cout << "CDerive::myDerive" << endl;
	}
};

int main(void)
{
	//上行的转换(派生类到基类的转换)
	shared_ptr<CDerive> spDeriveUp;
	shared_ptr<CBase> spBaseUp;
	spDeriveUp = make_shared<CDerive>();
	spBaseUp = dynamic_pointer_cast<CBase>(spDeriveUp);
	spBaseUp->myBase();

	//下行的转换(基类到派生类的转换)
	/*
	shared_ptr<CDerive> spDeriveDown;
	shared_ptr<CBase> spBaseDown;
	spBaseDown = make_shared<CBase>();
	spDeriveDown = dynamic_pointer_cast<CDerive>(spBaseDown);
	if (spDeriveDown == NULL)	//由于会进行类型的检查,这边是返回NULL
		cout << "spDeriveDown is null" << endl;
	*/

	shared_ptr<CDerive> spDeriveDown;
	shared_ptr<CBase> spBaseDown;
	spBaseDown = make_shared<CDerive>();
	spDeriveDown = dynamic_pointer_cast<CDerive>(spBaseDown);
	if (spDeriveDown == NULL)	//由于会进行类型的检查,这边是返回NULL
		cout << "spDeriveDown is null" << endl;
	spDeriveDown->myDerive();	

	return 0;
}

运行结果:

c++中dynamic_pointer_cast强制类型转换

相关标签: 强制类型转换