Returning a new object on the heap

[o360pfjN]

Hi all,

A quick one!

In the following code line:

virtual Mammal* Clone () {return new Cat(*this);}

I understanding that a new object is being created on the heap, and a pointer to it is being returned. But I don't understand why this code is valid, and I feel I should before moving on! The function is not returning a pointer, it is returning an object. What exactly is happening in order for the code to be valid?

Thanks :)

J

[Peter87]

new Cat(*this) gives you a pointer to the new cat object. The function returns the pointer. That's it.

[o360pfjN]

The (*this) referred to here is a parameter for a copy constructor...

Or is that not the pointer you are referring to? Do you mean another pointer which is provided as a result of creating the new Cat on the heap? Is there a conversion going on as a result of the return type?

lol clearly this will need to be spelt out a little :P

[SUH]

Your new object of cat is being created and its pointer is being returned (through Mammal* return type)...how could it possibly return an Object wen the return type is of pointer? Its not possible!

[vlad from moscow]

I'd like to point out that you can do this code more correct by returning pointer to a Cat object. That is

virtual Cat* Clone () const {return new Cat(*this);}
virtual Dog* Clone () const {return new Dog(*this);}

class Mammal
{
public:
   virtual !Mammal() = 0;
   virtual Mammal* Clone () const = 0;
};

Mammal::~Mammal() {}

class Cat: public Mammal
{
   virtual Cat* Clone () const { return new Cat( *this );}
};

class Dog: public Mammal 
{
   virtual Dog* Clone () const { return new Dog( *this ); }
}

[Gaminic]

@zuluisgrate:
You might be confused by the "*this", which is an object (a dereferenced pointer to an object, thus an object). However, the *this is simply a parameter for the constructor. The returned thing is actually the return value of "new Cat(<params>)", which is a Cat* (pointer!). Conceptually no different from doing "return new Cat(5);", but perhaps less confusing to look at.