问题描述
我很困惑这个。如何从操作符函数返回动态分配的对象?
考虑下面的例子:
I am quite confused about this. How to return a dynamically allocated object from operator function?Consider following example:
#include "stdafx.h"
#include <iostream>
#include "vld.h"
using std::cout;
class Point
{
public:
Point(int x,int y) : a(x),b(y)
{ }
Point()
{ }
Point operator + (Point p)
{
Point* temp=new Point();
temp->a=a+p.a;
temp->b=b+p.b;
Point p1(*temp); // construct p1 from temp
delete temp; // deallocate temp
return p1;
}
void show()
{
cout<<a<<' '<<b<<'\n';
}
private:
int a,b;
};
int main()
{
Point* p1=new Point(3,6);
Point* p2=new Point(3,6);
Point* p3=new Point();
*p3=*p2+*p1;
p3->show();
VLDEnable();
delete p1;
delete p2;
delete p3;
VLDReportLeaks();
system("pause");
}
我可以写这个程序没有额外的对象p1在这种情况下在重载的operator +功能?如何直接返回temp?
Can I write this program without extra object p1 in this case in overloaded operator + function? How Can I directly return temp?
您的帮助将非常感激。
请帮助我。 p>
Please help me.
推荐答案
Java语法和C ++之间有点混淆。在C ++中,除非你想要动态分配对象(在堆上),否则不需要 new
。只需使用
You are a bit confused between Java syntax and C++. In C++, there is no need for new
unless you want your objects to be dynamically allocated (on the heap). Just use
Point temp; // define the variable
// process it
return temp;
这样,你的本地对象将被创建在堆栈上,你不必
In this way, your local objects will be created on the stack, and you won't have to care about forgetting to delete
them etc.
从运算符+ 返回指针
Point* operator + (Point p)
{
Point* tmp = new Point;
// process
return tmp; // return the pointer to the dynamically-allocated object
}
code> operator +
,因为你不能链接它,即 a + b + c
这是因为 a + b
返回一个指针,然后 a + b + c
尝试调用 operator +
在一个指针上,没有定义。此外,还有更严重的问题,如在构建临时对象时分配内存泄漏,请参阅下面的@ Barry的注释。所以我希望我已经说服你返回的对象,而不是一个指针。
It actually breaks the operator+
, since you won't be able to chain it, i.e. a+b+c
won't work anymore.That's because a + b
returns a pointer, then a + b + c
tries invoking operator+
on a pointer, for which is not defined. Also, there are more serious issues, like leaking memory during the construction of your temporary objects in assignments, see @Barry's comment below. So I hope I have convinced you to return the object and not a pointer to it.
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