#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:
#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:
一些结论:
子类向基类转是一定没有问题的。基类转子类的话,必须基类的动态类型与要转换的子类一致。
原文链接: https://www.cnblogs.com/z1141000271/p/15357024.html
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