Question

我正在查看旧的考试问题以进行升级考试，其中一个问题是这样的：

//How many times is Foo's destructor called when func() is called?
void func(){
    Foo a;
    for (int i = 0; i < 10; i++){
        Foo *c = new Foo();
        a = *c;
    }
}

正确答案是1.有人可以向我解释为什么在for-loop中创建的每个新Foo都不会调用它一次吗？

Answer 1

使用new创建对象时，需要使用delete将其删除，以便调用析构函数并释放内存。因此，唯一会被调用析构函数的对象是a，它会在func结束时静态创建并销毁。

Answer 2

让我们看看您的代码实际在做什么：

<%=f.input :email, input_html: { autocomplete: 'email' } %>

如您所见，void func(){ Foo a; // Creates an object in the stack that will be destroyed once the function scope is no longer valid (meaning, when the function call is finished). for (int i = 0; i < 10; i++){ Foo *c = new Foo(); // this line allocates memory for a new object and stores a pointer to that memory in 'c' a = *c; // Makes a field-by-field copy (to put it simple) of the memory pointed by c into the object a. No new memory is allocated, no memory is destroyed } }分配的内存从未被破坏，您需要在某个时刻调用new Foo()来实现此目的。

为什么析构函数只在这里调用一次？

2 个答案: