有两个内存部分可以存储对象：
- 堆栈–堆栈中的内存由在块/函数内声明的所有成员使用。请注意， main 也是一个函数。
- 堆– 此内存未使用，可用于在运行时动态分配内存。
在块或函数内创建的对象的范围仅限于创建它的块。
- 在块内创建的对象将存储在堆栈中，当函数/block 退出时，对象将被销毁并从堆栈中移除。
- 但是如果我们在运行时创建对象，即通过动态内存分配，那么对象将被存储在堆上。这是在new运算符的帮助下完成的。在这种情况下，我们需要使用delete 运算符显式销毁对象。
例子：
Output:
Inside Block1...
length of rectangle is : 2
width of rectangle is :3
Destructor of rectangle
with the exit of the block, destructor called
automatically for the object stored in stack.
*********************************************
Inside Block2
length of rectangle is : 5
width of rectangle is :6
Destructor of rectangle
length of rectangle is : 0
width of rectangle is :0
下面是显示对象存储位置的程序：
// C++ program for required implementation
#include
using namespace std;
class Rectangle {
int width;
int length;
public:
Rectangle()
{
length = 0;
width = 0;
}
Rectangle(int l, int w)
{
length = l;
width = w;
}
~Rectangle()
{
cout << "Destructor of rectangle" << endl;
}
int getLength()
{
return length;
}
int getWidth()
{
return width;
}
};
int main()
{
// Object creation inside block
{
Rectangle r(2, 3); // r is stored on stack
cout << "Inside Block1..." << endl;
cout << "length of rectangle is : "
<< r.getLength() << endl;
cout << "width of rectangle is :"
<< r.getWidth() << endl;
}
cout << " with the exit of the block, destructor\n"
<< " called automatically for the object stored in stack."
<< endl;
/*
// uncomment this code and run once you will get
// the compilation error because the object is not in scope
cout<<"length of rectangle is : "<< r.getLength();
cout<< "width of rectangle is :" << r.getWidth();
*/
Rectangle* ptr2;
{
// object will be stored in heap
// and pointer variable since its local
// to block will be stored in the stack
Rectangle* ptr3 = new Rectangle(5, 6);
ptr2 = ptr3;
cout << "********************************************"
<< endl;
cout << "Inside Block2" << endl;
cout << "length of rectangle is : "
<< ptr3->getLength() << endl;
cout << "width of rectangle is :"
<< ptr3->getWidth() << endl;
// comment below line of code and
// uncomment *important line*
// and then check the object will remain
// alive outside the block.
// explicitly destroy object stored on the heap
delete ptr3;
}
cout << "length of rectangle is : "
<< ptr2->getLength() << endl;
cout << "width of rectangle is :"
<< ptr2->getWidth() << endl;
// delete ptr2; /* important line*/
return 0;
}
输出：
Inside Block1...
length of rectangle is : 2
width of rectangle is :3
Destructor of rectangle
with the exit of the block, destructor
called automatically for the object stored in stack.
********************************************
Inside Block2
length of rectangle is : 5
width of rectangle is :6
Destructor of rectangle
length of rectangle is : 0
width of rectangle is :0
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