Re: vectors and polymorphism
In article <1186514192.273353.140920@w3g2000hsg.googlegroups.com>,
<webmaster@developerland.com> wrote:
I have a vector with A and B elements on it , how can I retrieve B
elements only from col ?
class A
{
}
class B : public A
{
}
void main ()
{
std::vector<A*> col;
col.push_back (new A());
col.push_back (new B());
col.push_back (new A());
col.push_back (new A());
col.push_back (new B());
}
off the cuff:
struct save_B:std::iterator<std::output_iterator_tag,
void,void,void,void>
{
std::vector<B*> *out;
save_B(std::vector<B*> &a):out(&a){}
save_B & operator = (A *a)
{
B*b = dynamic_cast<B*>(a);
if(b) out->push_back(b);
return *this;
}
save_B & operator *() {return *this;}
save_B & operator ++() {return *this;}
save_B & operator ++(int) {return *this;}
};
//
std::vector<B*> Bs;
std:;copy(col.begin(),col.end(),save_B(Bs));
--
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