Best return type of an accessor to void*

[Brian Withun]

I have a base class (B) and several derived classes (D1, D2, ...)

I have a container class (C) with an attribute (void *d) which is
intended to point to any of D1, D2,...

My question is, on my C::GetObject() accessor, what is the most
appropriate return type?

void* C::GetObject( void ) { return d; }

or

B* C::GetD( void ) { return (B*) d; }


Is there any galvanizing rationale as to why I'd choose one return
type over the other, or is there yet another possibility I have not
considered?

TIA

Brian Herbert Withun

 

[Brian Herbert Withun]

I have a base class (B) and several derived classes (D1, D2, ...)

I have a container class (C) with an attribute (void *d) which is
intended to point to any of D1, D2,...

My question is, on myC::GetObject() accessor, what is the most
appropriate return type?

void*C::GetObject( void ) { return d; }

or

B*C::GetD( void ) { return (B*) d; }

Is there any galvanizing rationale as to why I'd choose one return
type over the other, or is there yet another possibility I have not
considered?

TIA

Brian Herbert Withun

[[disregard the C::GetD() above, my intended illustration is below]]


void* C::GetObject( void ) { return d; }

or

B* C::GetObject( void ) { return (B*) d; }

 

[Jim Langston]

I have a base class (B) and several derived classes (D1, D2, ...)

I have a container class (C) with an attribute (void *d) which is
intended to point to any of D1, D2,...

My question is, on my C::GetObject() accessor, what is the most
appropriate return type?

void* C::GetObject( void ) { return d; }

or

B* C::GetD( void ) { return (B*) d; }


Is there any galvanizing rationale as to why I'd choose one return
type over the other, or is there yet another possibility I have not
considered?

Your container class shoudl have an attribute of Base *d instead of a void*.

And, yes, return a B*

 

[Zachary Turner]

I have a base class (B) and several derived classes (D1, D2, ...)

I have a container class (C) with an attribute (void *d) which is
intended to point to any of D1, D2,...

Why isn't it a B*? If D1, D2, etc derive from B, make it a B*.

My question is, on my C::GetObject() accessor, what is the most
appropriate return type?

If you want ot be able to store things that are not always derived
from B, then another possibility is to make C a template class.

template<typename T>
class C
{
private:
//Some type of data structures to store multiple instances of T.
std::list<T*> internal_list; //example
std::vector<T*> internal_vec; //example

public:
T* GetObject();
};



Then you would create instances of C as follows:

C<D1> first;
D1* d1 = first.GetObject();

C<D2> second;
D2* d2 = second.GetObject();

C<NotDerivedFromB> third;
NotDerivedFromB* ndfb = third.GetObject();

 

[Victor Bazarov]

Oh, an there also a style mistake here. Please, drop the 'void'
between parentheses, it's so C.

Your container class shoudl have an attribute of Base *d instead of a
void*.
And, yes, return a B*

It would probably be worth mentioning that in the derived classes of
'C' (if any), you could even return a D1* or a D2* or..., since it
would be a *covariant* type.

V

 

[Brian Herbert Withun]

Your container class shoudl have an attribute of Base *d instead of a void*.

And, yes, return a B*

Thanks for the suggestion. I'm going to go this way because it has
that intangible measure of elegance, and it makes the purpose of the
code more evident when reading it for the first time. Upon reading
your response I had the experience of, "now why didn't *I* think of
that?"


Brian Herbert Withun