使用派生类的Ptr指向基类，反之亦然 [英] Using Ptr of derived class to point to base class and viceversa
问题描述
使用派生类的Ptr指向基类，反之亦然
类基础
{
....
}
等级派生：公共基础
{
....
}
我想知道使用它时的任何实际情况
a。 B b;
D * p =& b;
b。 B * b;
D d;
b =& d;
任何人都可以解释一下吗？我知道它是理论上OK.But我不能
为什么要这样做？
先谢谢，
Bhanu
Using Ptr of derived class to point to base class and viceversa
class base
{
....
}
class derived : public base
{
....
}
I want to know any practical scenario when this is used
a. B b;
D *p = &b;
b. B *b;
D d;
b = &d;
Can any one explain it?I know it is theoritically OK.But i am not able
why to do such things?
Thanks in Advance,
Bhanu
推荐答案
Bhan写道：
Bhan wrote:
使用派生类的Ptr指向基数上课和副课
班级基地
{
...
}类来源：公共基地
{
... }
我想知道使用它时的任何实际情况
a。 B b;
D * p =& b;
b。 B * b;
D d;
b =& d;
任何人都可以解释一下吗？我知道这是理论上的好。但我不能为什么要做这样的事情？
不会导致切片问题吗？
提前致谢，
Bhanu
Using Ptr of derived class to point to base class and viceversa
class base
{
...
}
class derived : public base
{
...
}
I want to know any practical scenario when this is used
a. B b;
D *p = &b;
b. B *b;
D d;
b = &d;
Can any one explain it?I know it is theoritically OK.But i am not able
why to do such things?
doesnt this lead to the Slicing Problem ?
Thanks in Advance,
Bhanu
placid写道：
Bhan写道：
Bhan wrote:
使用派生类的Ptr指向基类，反之亦然/>班级基础
{
...
}
班级派生：公共基地
{
...
} >
我想知道使用它时的任何实际情况
a。 B b;
D * p =& b;
没有实际使用非衍生类型的物体的向下转型。
b。 B * b;
D d;
b =& d;
Upcasting：一直都在发生。
任何人都可以解释一下吗？我知道这是理论上没问题。但我不能
为什么做这些事情？
Using Ptr of derived class to point to base class and viceversa
class base
{
...
}
class derived : public base
{
...
}
I want to know any practical scenario when this is used
a. B b;
D *p = &b;
No practical use of downcasting from an object not of the derived type.
b. B *b;
D d;
b = &d;
Upcasting: Happens all the time.
Can any one explain it?I know it is theoritically OK.But i am not able
why to do such things?
不会导致切片问题吗？
doesnt this lead to the Slicing Problem ?
复制对象时会发生切片。 OP只是将
指针指向该对象。
Slicing happens when you copy the object. The OP is simply taking
pointers to the object.
所以你的意思是通常使用它？
So you mean this is normally used?
Upcasting ：一直发生。
Upcasting: Happens all the time.
B b;
D * p =& b;
但是为什么这样做？为什么没有基地本身的ptr？（下）
B b;
B * p =& b;
你能否使用这两个？
B b;
B * p =& b;
D * p =& b;
B b;
D *p = &b;
But why do this ?why not have a ptr to base class itself ?(below)
B b;
B *p = &b;
Can you give the use of these two?
B b;
B *p = &b;
D *p = &b;
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