inheritnce

Mammal *pDog = new Dog;
here Mammal is base class and Dog is it's derived class

In such declaration destructor is not called why is it rule of C++?

Quote:

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Originally Posted by vkash

Mammal *pDog = new Dog;
here Mammal is base class and Dog is it's derived class

In such declaration destructor is not called why is it rule of C++?

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I don't understand your question. What do you mean by "the destructor is not called"?

You created a Dog object dynamically and assign it to a base class pointer. That's all that code does. Is it supposed to do something more than that?

Regards,

Paul McKenzie

Quote:

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Originally Posted by Paul McKenzie

I don't understand your question. What do you mean by "the destructor is not called"?

You created a Dog object dynamically and assign it to a base class pointer. That's all that code does. Is it supposed to do something more than that?

Regards,

Paul McKenzie

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OK compile this ode in visual c++


#include <iostream>
using std::cout;

class Mammal
{
public:
Mammal():itsAge(1) { cout << "Mammal constructor...\n"; }
~Mammal() { cout << "Mammal destructor...\n"; }
void Move() const { cout << "Mammal move one step\n"; }
void Speak() const { cout << "Mammal speak!\n"; }

protected:
int itsAge;
};

class Dog : public Mammal
{
public:
Dog() { cout << "Dog Constructor...\n"; }
~Dog() { cout << "Dog destructor...\n"; }
void WagTail() { cout << "Wagging Tail...\n"; }
void Speak()const { cout << "Woof!\n"; }
void Move()const { cout << "Dog moves 5 steps...\n"; }
};

int main()
{
Mammal *pDog = new Dog;
pDog->Move();
pDog->Speak();
return 0;
}

mammal and dog constructor called but their destructor not called at the end of main that is what i want to ask you
t

Quote:

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mammal and dog constructor called but their destructor not called at the end of main that is what i want to ask you

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Code:

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Mammal *pDog = new Dog;

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You aren't deleting pDog.

Code:

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delete pDog

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Now the descructor will be called. Remember, C++ doesn't do garbage collection like Java does.

Quote:

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Originally Posted by vkash

mammal and dog constructor called but their destructor not called

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That is because in C++, you must call "delete" for every call to "new" you make.

Secondly, your base class destructor must be virtual for the delete to work correctly.

Regards,

Paul McKenzie

Quote:

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Originally Posted by vkash

mammal and dog constructor called but their destructor not called at the end of main that is what i want to ask you

---

You are responsible for deleting objects that you allocate.
But my guess is that you will have another question after you add

Code:

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delete pDog;

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Inheritance has nothing to do with this. Every new must have a matching delete, no matter whether the types being created are related by inheritance or not.

thanks to all of you i got the point that is -> I have created pDog so i am responsible for their deletion destructor will called when i write delete pDog; in my code.
once again thanks to all of you.

Hi,

Just to clarify, as Paul pointed out the Dog destructor will only be called if the Mammal destructor is declared as virtual (which it isn't in the code that you posted.)

Alan