我有一个简单的容器类,指向一个抽象类,我有函数来获取/设置容器类中的指针。更具体地说,这个类看起来像这样:C++将抽象类的派生对象添加到另一个类中而没有悬挂指针?
class Container
{
Abstract* thing;
public:
void set(Abstract &obj)
{
thing = &obj; //danger of dangling pointer
}
Abstract* get()
{
return thing;
}
};
Abstract
是一个抽象类。如已经看到的那样,存在悬挂指针的危险。我知道我可以制作一个对象(新)的副本,然后指向它。但是我不能创建一个抽象类的实例。有什么解决方案?
以下只是更多信息:
类定义
class Abstract
{
public:
virtual void something() = 0;
};
class Base : public Abstract
{
int a;
public:
Base() {}
Base(int a) : a(a){}
virtual void something()
{
cout << "Base" << endl;
}
};
class Derived : public Base
{
int b;
public:
Derived() {}
Derived(int a, int b) : Base(a), b(b){}
virtual void something()
{
cout << "Derived" << endl;
}
};
简单的测试
void setBase(Container &toSet)
{
Base base(15);
toSet.set(base);
}
void setDerived(Container &toSet)
{
Derived derived(10, 30);
toSet.set(derived);
}
int main()
{
Container co;
Base base(15);
Derived derived(10, 30);
Base *basePtr;
Derived *derivedPtr;
//This is fine
co.set(base);
basePtr = static_cast<Base *>(co.get());
basePtr->something();
//This is fine
co.set(derived);
derivedPtr = static_cast<Derived *>(co.get());
derivedPtr->something();
//Reset
basePtr = nullptr;
derivedPtr = nullptr;
//Dangling pointer!
setBase(co);
basePtr = static_cast<Base *>(co.get());
basePtr->something();
//Dangling pointer!
setDerived(co);
derivedPtr = static_cast<Derived *>(co.get());
derivedPtr->something();
return 0;
}
护理分享downvote的原因是什么? – silentwf
的可能的复制[什么是智能指针,当我应该使用一个?(http://stackoverflow.com/questions/106508/what-is-a-smart-pointer-and-when-should-i-use - 酮) – LogicStuff
@silentwf的downvote原因的提示,当你悬停鼠标指针的DV按钮共享。 –