引用派生类的指针 [英] reference to pointer of derived class

问题描述

struct Base {

};


struct派生：public Base {

};


void f（基数* pBase）

{

派生* pDerived =（派生*）pBase;

}


有没有办法让pDerived引用pBase？

解决方案

" Moes" <公顷*** @ cd.com>在消息中写道

news：35 ************* @ individual.net ...

struct Base {
} ;

struct派生：公共基地{
};

void f（Base * pBase）
{
Derived * pDerived =（派生*）P基准;


我猜你写的那个演员要沉默

编译器警告。你真的想做什么？
要做什么？ （以上并不是你可能会做的事情。）b $ b b）。研究'切片''。

}

有没有办法让pDerived引用pBase？

从语法上讲，是的，但我想我们应该首先确定

，如果这真的是你需要的话。你想做什么？


-Mike

" Mike Wahler" < MK ****** @ mkwahler.net>在消息中写道

新闻：Ky ***************** @ newsread3.news.pas.earthl ink.net ...

Moes <公顷*** @ cd.com>在消息中写道
新闻：35 ************* @ individual.net ...

struct Base {
};

struct Derived：public Base {
};

void f（Base * pBase）
{
Derived * pDerived =（Derived *）pBase ;

我猜你写的那个演员要沉默
一个编译器警告。你真的想做什么？ （以上并不是你想的那样）。研究'切片''。

}

有没有办法让pDerived引用pBase？

我正在努力让演员尽可能高效地进行演出，所以我想了

a参考会比副本快。也许我应该提到Base

是一个纯虚拟类，并且f会将pBase转换为从Base派生的多个类之一

，具体取决于上下文。 />

" MOES" <公顷*** @ cd.com>在消息中写道

新闻：35 ************* @ individual.net ...

Mike Wahler ; < MK ****** @ mkwahler.net>在消息中写道
新闻：Ky ***************** @ newsread3.news.pas.earthl ink.net ...

< br>Moes <公顷*** @ cd.com>在消息中写道
新闻：35 ************* @ individual.net ...

struct Base {
};

struct Derived：public Base {
};

void f（Base * pBase）
{
Derived * pDerived =（Derived *）pBase ;
我猜你写的那个演员要沉默
一个编译器警告。你真的想做什么？ （以上并不是你想的那样）。研究'切片''。

}

有没有办法让pDerived引用pBase？

我正在尝试尽可能高效地进行演员表演，

你误解了我的问题。为什么你觉得你需要

将''Base *''转换为''Derived *''？我问，''你想要实现的是什么？'，而不是''描述你是如何实现它的''

a参考会更快比副本。也许我应该提到Base
是一个纯虚拟类，f会将pBase转换为从Base派生的一些
类中的一个，

但为什么呢？需要降低imo对设计的怀疑。


-Mike

struct Base{
};

struct Derived: public Base{
};

void f( Base *pBase )
{
Derived *pDerived = (Derived*)pBase;
}

Is there any way to make pDerived a reference to pBase?

解决方案

"Moes" <ha***@cd.com> wrote in message
news:35*************@individual.net...

struct Base{
};

struct Derived: public Base{
};

void f( Base *pBase )
{
Derived *pDerived = (Derived*)pBase;
I''ll guess that you wrote that cast to silence
a compiler warning. What are you really trying
to do? (The above doesn''t do what you probably
think). Research ''slicing''.
}

Is there any way to make pDerived a reference to pBase?

Syntactically, yes, but I think we should first determine
if that''s really what you need. What are you trying to do?

-Mike

"Mike Wahler" <mk******@mkwahler.net> wrote in message
news:Ky*****************@newsread3.news.pas.earthl ink.net...

"Moes" <ha***@cd.com> wrote in message
news:35*************@individual.net...

struct Base{
};

struct Derived: public Base{
};

void f( Base *pBase )
{
Derived *pDerived = (Derived*)pBase;

I''ll guess that you wrote that cast to silence
a compiler warning. What are you really trying
to do? (The above doesn''t do what you probably
think). Research ''slicing''.

}

Is there any way to make pDerived a reference to pBase?

Syntactically, yes, but I think we should first determine
if that''s really what you need. What are you trying to do?

I''m trying make the cast to pDerived as efficient as possible, so I figured
a reference would be faster than a copy. Maybe I should mention that Base
is a pure virtual class, and f will cast pBase to one of a number of classes
derived from Base, depending on context.

"Moes" <ha***@cd.com> wrote in message
news:35*************@individual.net...

"Mike Wahler" <mk******@mkwahler.net> wrote in message
news:Ky*****************@newsread3.news.pas.earthl ink.net...

"Moes" <ha***@cd.com> wrote in message
news:35*************@individual.net...

struct Base{
};

struct Derived: public Base{
};

void f( Base *pBase )
{
Derived *pDerived = (Derived*)pBase;
I''ll guess that you wrote that cast to silence
a compiler warning. What are you really trying
to do? (The above doesn''t do what you probably
think). Research ''slicing''.

}

Is there any way to make pDerived a reference to pBase?

Syntactically, yes, but I think we should first determine
if that''s really what you need. What are you trying to do?

I''m trying make the cast to pDerived as efficient as possible,

You misunderstand my question. Why do you feel you need to
convert a ''Base *'' to a ''Derived *''? I was asking, ''what are
you trying to achieve'', not ''describe how you''re trying to achieve it''
a reference would be faster than a copy. Maybe I should mention that Base
is a pure virtual class, and f will cast pBase to one of a number of classes derived from Base,

But why? The need for downcasting imo casts much suspicion upon
the design.

-Mike

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