C ++：我可以投射一个向量< derived_class>到向量< base_class>在函数调用期间？ [英] C++: Can I cast a vector <derived_class> to a vector <base_class> during a function call?

问题描述

我有一个存在的类和函数，如下所示：

  class base_class {
 ... 
} 
 
 void Func（...，vector< base_class>& vec_b，...）{
 //在函数内部，矢量vec_b正被重组并重新调整大小
} 
  

，我定义了一个派生类， p>

 类derived_class：public base_class {
 ... 
} 
  

现在，不改变函数 Func ，我可以传递向< derived_class> 中插入到，例如：

 $ c> void main（）{
 vector< derived_class> d; 
 Func（...，d，...）; 
} 
  

，使得派生类 d 经历相同的重组和重新调整大小？
我知道我可以将派生类转换为基类在一个函数调用没有问题，但一旦用向量进行播放，似乎有困难？我找不到在线的答案，所以任何建议或帮助是非常感谢。感谢。

解决方案

否。即使A是B，向量< A> 不是向量< B> 。 >



要传递一个代替另一个，你可以传递指针的向量（或使用Boost ptr_vector）。或者，您也可以使用模板来传递任何提供正确界面的矢量。

这两个都需要改变您的功能 - 基本上没有办法避免（仍然提供你想要的功能）。

I have a existed class and function which look like this:

Class base_class{
    ...
}

void Func(...,vector<base_class> &vec_b,...){
    // inside the function, the vector vec_b is being re-organized and re-sized
}

and I defined a derived class which looks like:

Class derived_class: public base_class{
    ...
}

Now, without changing the function Func, can I pass a vector<derived_class> into Func, ex:

void main(){
    vector <derived_class> d;
    Func(...,d,...);
}

such that the derived class d undergoes the same re-organizing and re-sizing? I know I can cast derived class to base class in a function call with no problem, but once with a vector into play, there seems to be difficulties? I can't find the answer online, so any suggestions or help is greatly appreciated. thanks.

解决方案

No. Even if an A is a B, a vector<A> is not a vector<B>.

To pass one in place of the other, you can pass a vector of pointers (or use a Boost ptr_vector). Alternatively, you may be able to use a template to allow passing a vector of anything that provides the right interface.

Either of these will require changing your function though -- there's essentially no way to avoid that (and still provide the functionality you want).

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