Re: Why can't pass vector of "Derived" to function that takes vector of "Base"?

On Apr 28, 6:05 pm, Rob <someidunknown1...@[EMAIL PROTECTED]
> wrote:
> I have these cl***** (elided methods):
>
> class Base
> {
> public:
>       Base(string name) {...}
>
> };
>
> class Derived : public Base
> {
> public:
>       Derived(String name) : Base( name ) {...}
>
> };
>
> And neither of these work:
>
>       /*** ATTEMPT ONE **/
>       void create(std::vector<Base>& arr)
>       {
>             ...
>       }
>
>       int main()
>       {
>            std::vector<Derived> arr;
>            create( arr );
>       }
>
>       /*** ATTEMPT TWO **/
>       void create(std::vector<Base*>& arr)
>       {
>             ...
>       }
>
>       int main()
>       {
>            std::vector<Derived*> arr;
>            create( arr );
>       }

vector<Base> and vector<Derived> are unrelated types.
They are not connected by inheritance like the types they
contain, so they don't behave polymorphically. Example:

class B {};
class D: public B {};

struct A { class B b; };
struct C { class D d; };

C c;
A& a( c ); // ERROR

You can insert Derived into vector<Base>, and Derived*
into vector<Base*> though (with slicing in the first case)

-- 
  Nikolai

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