CODEWITHSUNDEEP
c++classdelete-operator
UnknownError1337
UnknownError1337

Reputation: 1222

Delete inside of class

I got some weird problem. I use delete operator inside of class method and I want to know how solve this problem.

This is code:

#include <iostream>

using namespace std;

class A
{
    public:
        int a;

        ~A() {
            cout << "call ~A()" << endl;
        }

        void action()
        {
            /* code here */
            delete this; //this line depends on some if statements
            /* code here */
        }

        void test2() {
            cout << "call test2()" <<  a << endl;
        }

        void test() {
            a = 10;
            cout << "call test()" << endl;

            action();

            //how can I check if data is deleted?
            test2();
        }
};

int main()
{

    A* a = new A();
    a->test();

}

How can I check if data is deleted by delete operator? Is it even possible?

Upvotes: 0

Views: 941

Answers (2)

&#214;&#246; Tiib
&#214;&#246; Tiib

Reputation: 10979

In C++ there are other return values available than void. Therefore your action can return something that indicates if this has been deleted or not.

Note that you should not access any non-static data members or call any non-static member functions after deleteing this. Some people feel it to be difficult to guarantee so they ban delete this altogether.

Note to opponents that C++ FAQ claims that delete this is legal construct and I haven't also found anything forbidding it.

Upvotes: 3

Mats Petersson
Mats Petersson

Reputation: 129374

  1. Using delete this; is nearly always "bad". There are exceptions, but those are really unusual. Think about what you are trying to do. Most of the time, this means that you should have a wrapper object and an inner object that is created/deleted by the wrapper object.

  2. You can't check if something has been deleted (in a reliable way/portable way). In your particular test-case, you are exercising "undefined behaviour" by "using an object after it has been destroyed", which means you can't really tell what is going to happen. You have to trust the C++ runtime that delete does what it says on the label.

Upvotes: 5

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