在C ++中shared_ptr的确切用途是什么? [英] What is the exact use of shared_ptr in c++?

问题描述

为什么我们使用shared_ptr?

Why we use shared_ptr?

<br />
<br />
<pre lang="xml">#include<iostream><br />
#include<memory><br />
#include <vector><br />
<br />
using namespace std;<br />
class x<br />
{<br />
    public:<br />
    int i;<br />
    x():i(12323123)<br />
    {<br />
        cout<<"constructor called"<<endl;<br />
    }<br />
    ~x()<br />
    {<br />
        cout<<"destructor called"<<endl;<br />
    }<br />
};<br />
    vector< shared_ptr<x> > testvec;<br />
<br />
int test()<br />
{<br />
        shared_ptr<x> n(new x);<br />
            testvec.push_back((n));<br />
}<br />
<br />
main()<br />
<br />
{<br />
    test();<br />
    vector< shared_ptr<x> > tests=((testvec));<br />
    cout<<(*(tests.at(0))).i;<br />
}</pre>

推荐答案

它用于消除应用程序中内存泄漏的风险，因为您不需要记得在完成操作后手动删除指针.

It is used to remove the risk of memory leakage in an application, because you don''t need to remember to manually delete the pointer when you a re done with it.

我假设使用了shared_ptr而不是unique_ptr，以便能够从该向量获得对象的副本，并且仍然具有正确的引用计数对于每个对象.

所以对于代码:

I assume shared_ptr is used rather than unique_ptr to be able to have copies of objects from that vector and still have correct reference count for each object.

so for code:

shared_ptr<x> variable = new x;
{
    vector< shared_ptr<x> > arr;
    arr.push_back(x)
}
</x></x>

在方括号变量中的引用计数等于2，否则等于1.

in the brackets variable will have ref count equal to 2, and equal to 1 otherwise.

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