can i call a destructor inside a constructor in c++??

[Praveen30]

Normally we define the constructor and destructor seperately...i want to know is there any way by which i can call destructor inside a constructor and if it is possible then what will be the effect on the object??



class A
{
int x;
public:

A{
~A() // can i do something like this???
}
};

int main()
{
A obj; // if this happens then what will be the effect on object???
return 0;
}

[matt_symes]

Hi


can i call a destructor inside a constructor in c++??
i want to know is there any method by which we can define the destructor inside a constructor

Which one are you trying to do ?

Kind regards

[Praveen30]

Hi



Which one are you trying to do ?

Kind regards

sorry for this confusion...take the first one...i just want to know can a destructor be called inside a constructor??

[dwhitney67]

... is there any way by which i can call destructor inside a constructor

Umm, why would you want to do this? I'm not sure if the compiler will allow it, but you can try.

[Simian Man]

Of course you can. C++ lets you do anything you want to no matter how stupid it is. Consider:


#include <iostream>
using std::cout;

class A {
public:
A( ) {
cout << "Starting Constructor\n";
this->~A( );
cout << "Leaving Constructor\n";
}

~A( ) {
cout << "In Destructor\n";
}
};

int main( ) {
A a;
return 0;
}


The more important question is should you call the destructor in the constructor and the answer is no. Destructors are automatically called for you and should never be called more than once. Therefore you should never call it yourself. See the C++ FAQ Lite (http://www.parashift.com/c++-faq-lite/dtors.html) for more info.

[Praveen30]

Of course you can. C++ lets you do anything you want to no matter how stupid it is. Consider:


#include <iostream>
using std::cout;

class A {
public:
A( ) {
cout << "Starting Constructor\n";
this->~A( );
cout << "Leaving Constructor\n";
}

~A( ) {
cout << "In Destructor\n";
}
};

int main( ) {
A a;
return 0;
}
The more important question is should you call the destructor in the constructor and the answer is no. Destructors are automatically called for you and should never be called more than once. Therefore you should never call it yourself. See the C++ FAQ Lite (http://www.parashift.com/c++-faq-lite/dtors.html) for more info.

thanks. ya, i know the question is stupid..but somebody asked me so i just want to know the answer..

[dwhitney67]

And here is a case where calling the destructor manually leads to disaster:


class Foo
{
public:
Foo()
: value(new int(10))
{
this->~Foo();
}
~Foo()
{
delete value;
}
private:
int* value;
};

int main()
{
Foo foo;
}

Of course, one can be a little more careful; for instance, setting the pointer to null after it has been deleted. But typically this is not done within the destructor.