问：如何复制多态类？ [英] Q: How to copy a polymorphic class?

问题描述

--- foo.h ---

class foo

{

public：

虚拟空虚DoStuff（无效）;

虚拟~foo（）;

};


--- bar.h ---

#include" foo.h"

class bar：public foo

{

public：

virtual void DoStuff（void）;

};


--- bloggs.cpp ---


#include" foo.h"

extern void Bloggs（foo * myFoo）

{

foo * localFoo = new foo（* myFoo）;

localFoo-> DoStuff（）;

删除localFoo;

}


--- main.cpp ---

#include" bar.h"

#include " bloggs.h"

int main（int argc，char * argv []）

{

bar myBar;

Bloggs（& myBar）;

返回0;

}


在上面的代码中，在functionBloggs，localFoo是一个foo副本

由foo par构造我传入的条形参数。


而不是这个，我想复制完整的bar参数并将

结果分配给localFoo。有没有办法在没有bloggs.cpp的情况下这样做？
需要#include" bar.h"？ （我想我需要一些类似于

的虚拟拷贝构造函数......）

-

Simon Elliott
http://www.ctsn.co.uk/

解决方案

Simon Elliott写道：

（我想我需要一些类似于
虚拟拷贝构造函数...）

是：


派生*派生:: create_new（）

{

返回新的Derived（* this）;

}

lilburne写道：

Simon Elliott写道：

（我想我需要一些类似于
虚拟拷贝构造函数的东西......）

是的：

Derived * Derived :: create_new（）
{
返回new Derived（* this）;
}

当然每个派生类都会需要这个功能，并且它会在基类中需要虚拟或纯虚拟，并且它应该是

const。此外，clone（）是一个更广泛使用（也更合适）的名称

。

lilburne< li ******@godzilla.net>写道

（我想我需要一些类似于
虚拟拷贝构造函数的东西......）

是：

Derived * Derived :: create_new（）
{
返回new Derived（* this）;
}

非常好。这将很好地完成工作。

-

Simon Elliott
http://www.ctsn.co.uk/


blockquote>

--- foo.h ---
class foo
{
public:
virtual void DoStuff(void);
virtual ~foo();
};

--- bar.h ---
#include "foo.h"
class bar:public foo
{
public:
virtual void DoStuff(void);
};

--- bloggs.cpp ---

#include "foo.h"
extern void Bloggs(foo* myFoo)
{
foo* localFoo = new foo(*myFoo);
localFoo->DoStuff();
delete localFoo;
}

--- main.cpp ---
#include "bar.h"
#include "bloggs.h"
int main(int argc, char* argv[])
{
bar myBar;
Bloggs (&myBar);
return 0;
}

In the code above, In the function "Bloggs", localFoo is a foo copy
constructed from the foo part of the bar argument I passed in.

Instead of this, I want to copy the complete bar argument and assign the
result to localFoo. Is there any way of doing this without bloggs.cpp
needing to #include "bar.h"? (I suppose I need something analogous to a
virtual copy constructor...)
--
Simon Elliott
http://www.ctsn.co.uk/

解决方案

Simon Elliott wrote:

(I suppose I need something analogous to a
virtual copy constructor...)

Yes:

Derived* Derived::create_new()
{
return new Derived(*this);
}

lilburne wrote:

Simon Elliott wrote:

(I suppose I need something analogous to a
virtual copy constructor...)

Yes:

Derived* Derived::create_new()
{
return new Derived(*this);
}

Of course every derived class would need that function, and it would
need to be virtual or pure virtual in the base class, and it should be
const. Also, clone() is a more widely used (and more appropriate) name
for it.

lilburne <li******@godzilla.net> writes

(I suppose I need something analogous to a
virtual copy constructor...)

Yes:

Derived* Derived::create_new()
{
return new Derived(*this);
}

Excellent. That will do the job nicely.
--
Simon Elliott
http://www.ctsn.co.uk/

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