对象指针向量上的 vector::erase() 是否会破坏对象本身?

2021-12-21 00:00:00 vector c++ stl

我有一个指向对象的指针向量.我需要从向量中删除一个元素并将该元素放在另一个列表中.

I have a vector of pointers to objects. I need to remove an element from the vector and place that element in another list.

我读到擦除可用于从向量中删除对象，但我也读到它在这样做之前调用了对象析构函数.

I read that erase can be used to remove the object from the vector, but I also read that it calls the objects destructor before doing so.

我需要知道擦除对象是否也会破坏它.

I need to know whether or not erasing the object will destroy it as well.

推荐答案

vector::erase
从向量容器中移除并调用其析构函数，但如果包含的对象是一个指针，则它不会拥有销毁它的所有权.

vector::erase
Removes from the vector container and calls its destructor but If the contained object is a pointer it doesnt take ownership of destroying it.

您必须对每个包含的指针显式调用 delete 以删除它指向的内容，例如:

You will have to explicitly call delete on each contained pointer to delete the content it is pointing to, for example:

void clearVectorContents( std::vector <YourClass*> & a ) 
{    
    for ( int i = 0; i < a.size(); i++ ) 
    {       
        delete a[i];    
    }    
    a.clear(); 
}

在标准容器中存储原始指针不是一个好主意.如果你真的需要存储必须由new分配的资源，那么你应该使用boost::shared_ptr.查看 Boost 文档.

Storing raw pointers in standard containers is not a good idea. If you really need to store resources that have to be allocated by new, then you should use boost::shared_ptr. Check out the Boost documentation.

更通用的 &优雅的解决方案:
此解决方案使用 for_each &templates 正如@Billy 在评论中指出的:

An more generic & elegant solution:
This solution makes use of for_each & templates as @Billy pointed out in comments:

// Functor for deleting pointers in vector.
template<class T> class DeleteVector
{
    public:
    // Overloaded () operator.
    // This will be called by for_each() function.
    bool operator()(T x) const
    {
        // Delete pointer.
        delete x;
        return true;
    }
};

这可以称为:

for_each( myclassVector.begin(),myclassVector.end(),
          DeleteVector<myclass*>());

其中，myclassVector 是包含指向 myclass 类对象的指针的向量.

where, myclassVector is your vector containing pointers to myclass class objects.

用法示例:

#include "functional"
#include "vector"
#include "algorithm"
#include "iostream"

//Your class
class myclass
{
    public:
        int i;
        myclass():i(10){}
};


// Functor for deleting pointers in vector.
template<class T> class DeleteVector
{
    public:
    // Overloaded () operator.
    // This will be called by for_each() function.
    bool operator()(T x) const
    {
        // Delete pointer.
        delete x;
        return true;
    }
};


int main()
{
    // Add 10 objects to the vector.
    std::vector<myclass*> myclassVector;

    for( int Index = 0; Index < 10; ++Index )
    {
        myclassVector.push_back( new myclass);
    }

    for (int i=0; i<myclassVector.size(); i++) 
    {
        std::cout << " " << (myclassVector[i])->i;
    }

    // Now delete the vector contents in a single  line.
    for_each( myclassVector.begin(),
              myclassVector.end(),
              DeleteVector<myclass*>());

    //Clear the vector 
    myclassVector.clear();

    std::cout<<"
"<<myclassVector.size();

    return 0;
}

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