为什么类的析构器调用了两次？ [英] Why is the destructor of the class called twice?

问题描述

如果问题听起来很愚蠢，我表示歉意，我是在跟随SO的专家，自己尝试一些例子，这是其中之一。我没有尝试搜索选项，但没有找到这样的答案。

Apologies if the question sounds silly, I was following experts in SO and trying some examples myself, and this is one of them. I did try the search option but didn't find an answer for this kind.

class A
{
    public:
         A(){cout<<"A Contruction"<<endl;}
        ~A(){cout<<"A destruction"<<endl;}
};

int main()
{
    vector<A> t;
    t.push_back(A()); // After this line, when the scope of the object is lost.
}

为什么类的析构函数调用两次？

Why is the destructor of the class called twice ?

推荐答案

要添加元素，在临时对象上调用复制构造函数。在 push_back（）后，临时对象被销毁 - 这是第一个析构函数调用。然后向量实例超出范围并销毁所有存储的元素 - 这是第二个析构函数调用。

To add the element a copy constructor is invoked on a temporary object. After the push_back() the temporary object is destroyed - that't the first destructor call. Then vector instance goes out of scope and destroys all the elements stored - that's the second destructor call.

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