C ++如何在不删除对象的情况下将对象存储在数组中

Question

我想就我在学习C++时遇到的这个问题寻求帮助。我试图将对象直接存储到数组中，但意识到对象会立即被解构。我想不通为什么会这样。

#include <iostream>

class Thing{
    public:
    ~Thing(){
        std::cout<<"Thing destructing";
    }
};

int main(){
    Thing arr[1];
    arr[0] = Thing();
    int x;
    std::cin>>x;
};

Answer 1

在此声明中

arr[0] = Thing();

使用默认的复制赋值运算符将此表达式创建的临时对象Thing()分配给数组的元素。分配后临时对象被销毁。

为了更清楚运行这个演示程序。

#include <iostream>

class Thing
{
public:
    ~Thing()
    {
        std::cout<<"Thing " << i << " destructing\n";
    }
    
    Thing & operator =( const Thing & )
    {
        std::cout << "Thing " << i << " assigning\n";
        return *this;
    }
    
    Thing() : i( ++n )
    {
        std::cout << "Thing " << i << " constructing\n";
    }

private:    
    size_t i;
    static size_t n;
};

size_t Thing::n = 0;

int main() 
{
    {
        Thing arr[1];
        arr[0] = Thing();
    }
    
    std::cin.get();
    
    return 0;
}

它的输出是

Thing 1 constructing
Thing 2 constructing
Thing 1 assigning
Thing 2 destructing
Thing 1 destructing

Answer 2

假设您还不知道。

智能指针

#include <memory>

// ...

int main() {
    std::shared_ptr<Thing> arr[1];
    arr[0] = std::shared_ptr<Thing>(new Thing());

    // ...

    // <-- Is automatically deleted around here.
}

指针

不推荐；使用指针看起来像：

int main() {
    Thing *arr[1] = {};
    arr[0] = new Thing();

    int x;
    std::cin >> x;

    // WARNING: remember to manually delete.
    delete arr[0];
} // <-- BTW, you don't need semi-colon.

C ++如何在不删除对象的情况下将对象存储在数组中

C++ How to store object in arrays without them deleted

c++

class

destructor

temporary-objects

copy-assignment

智能指针

指针