从向量复制<指针*>到向量<指针*>在 C++ 中 [英] Copy from vector&lt;pointer*&gt; to vector&lt;pointer*&gt; in C++

问题描述

我创建了一个向量 A 并想使用以下方法复制到另一个类中的向量 B，这是正确的方法吗?向量 A 可能会被破坏！我在谷歌搜索，但没有找到好的解决方案和有意义的解释.谢谢大家

void StateInit(vector listBtn){_m_pListBtn = listBtn;};

解决方案

是与否，您正在按值传递向量:

void StateInit(vector listBtn){_m_pListBtn = listBtn;};

这意味着 listBtn 是向量 A 的副本(假设我们正在调用作为 StateInit 参数传递的向量 A)，如果删除向量 A，向量 B 仍将拥有指针集合，并且它们将有效，因为指针向量的销毁不会删除指向的对象，因为现在不可能如何(应该调用、删除、删除 []、释放?).

请记住，如果您修改/删除向量 A 中的元素之一(使用向量上的指针)，则该元素将在向量 B 中修改(因为它是指向同一元素的指针).

我不确定你的意图是什么，但如果你想复制整个向量，你应该为对象实现一个克隆机制，然后使用变换复制它们:

class cloneFunctor {民众:T* operator() (T* a) {返回 a->clone();}}

那就:

void StateInit(vector listBtn){变换(listBtn.begin()，listBtn.end()，back_inserter(_m_pListBtn)，cloneFunctor())；};

如果您的意图不是克隆它而是共享指针，您应该将向量作为指针或引用传递:

void StateInit(const vector& listBtn){_m_pListBtn = listBtn;};

I create a vector A and want to copy to a vector B in another class by using below method, is it a correct way? The vector A may be destroyed! I searched in google, but not found the good solution and meaningful explanation. Thanks everyone

void  StateInit(vector<CButton*> listBtn) 
{ 
   _m_pListBtn = listBtn; 
 };

解决方案

Yes and no, you are passing the vector by value:

void  StateInit(vector<CButton*> listBtn) 
{ 
   _m_pListBtn = listBtn; 
 };

Wich means that listBtn is a copy of vector A (asuming we are calling vector A the one passed as parameter of StateInit), if you delete vector A, vector B will still have the collection of pointers and they will be valid since the destruction of a vector of pointers doesnt delete the pointed objects because it cant possible now how (should it call, delete, delete[], free?).

Do keep in mind that if you modify/delete one of the elements from vector A (using the pointers on the vector), that element will be modified in vector B (since its a pointer to the same element).

Im not sure what is your intend with this, but if you want to copy the whole vector, you should implement a clone mechanism for the objects and then copy them using transform:

class cloneFunctor {
public:
    T* operator() (T* a) {
        return a->clone();
    }
}

Then just:

void  StateInit(vector<CButton*> listBtn) 
{ 
   transform(listBtn.begin(), listBtn.end(), back_inserter(_m_pListBtn), cloneFunctor()); 
 };

IF your intention is not to clone it but to share the pointers you should pass the vector as pointer or reference:

void StateInit(const vector<CButton*>& listBtn) 
{ 
   _m_pListBtn = listBtn; 
};

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