c++ how to delete a class via pointer to the class

Question

Somewhere in my code I call: A* p = new A; and I put the pointer p in a vector.

Now I want to delete the pointer and the class the pointer is pointing to. like this:

A* p = getpointerfromvector(index); // gets the correct pointer

Delete the pointer from the vector:

vector.erase(vector.begin()+index)

Now I want to delete the class the pointer is pointing to and delete it.

delete p; // (doest work: memorydump)

or p->~A with ~A the destructor of class A with body: delete this;. (my program quits whenever I call the function.)

A small clarification on nomenclature: In your case A is the name of a class, while p is a pointer to an object. When you do new A you are creating a new object, not a new class. It is important to keep the notions of class and object separate :) — Magnus Hoff
– Magnus Hoff, Commented Nov 13, 2013 at 16:58
Please show a complete, compilable example that demonstrates the problem. — Benjamin Lindley
– Benjamin Lindley, Commented Nov 13, 2013 at 17:00
delete p is correct. If it doesn't work, post an sscce demonstrating the problem. — interjay
– interjay, Commented Nov 13, 2013 at 17:00

enhzflep · Accepted Answer · 2013-11-13 17:08:10Z

2

This works for me. Cant compare it to your code since its not all in your post.

#include <stdio.h>
#include <vector>

using std::vector;

class A
{
public:
    A() {mNum=0; printf("A::A()\n");}
    A(int num) {mNum = num; printf("A::A()\n");}
    ~A() {printf("A::~A() - mNum = %d\n", mNum);}
private:
    int mNum;
};

int main ()
{
    A *p;
    vector <A*> aVec;
    int i, n=10;
    for (i=0; i<n; i++)
    {
        p = new A(i);
        aVec.push_back(p);
    }
    int index = 4;
    p = aVec[index];
    aVec.erase(aVec.begin()+index);
    delete(p);
}

Output:

A::A()
A::A()
A::A()
A::A()
A::A()
A::A()
A::A()
A::A()
A::A()
A::A()
A::~A() - mNum = 4

answered Nov 13, 2013 at 17:08

enhzflep

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2 Comments

user2321611 Over a year ago

I forgot to change my destructor to ~A{} instead of ~A{delete this}

enhzflep Over a year ago

Easily done. It's for just these kinds of oversights, that you should always aim to post an SSCCE - Short Self Contained Correct (Compilable) Example. (sscce.org)

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