Re: pointers and references to automatic variables :( how to do a good builder pattern implementation?
On 30 juil, 22:51, Diego Martins <jose.di...@gmail.com> wrote:
void whateverUB()
{
MyInterface * blah;
if( some computation ) {
MyDerived1 a(parameters depending of computation);
blah = &a;
} else {
other computation
MyDerived2 b(other parameters depending of other computation);
blah = &b;
}
blah->execute();
}
You do not need to use dynamic memory allocation.
const MyInterface& blah = some_compution ? MyDerived1(parameters) :
MyDerived2(parameters);
blah.execute();
Other possibility, but that requires copying, since variant doesn't
have in-place construction at the moment:
template<typename Base>
struct get_base : boost::static_visitor<Base&>
{
template<typename T>
Base& operator()(T& t) const
{
return t;
}
};
boost::optional< boost::variant<MyDerived1, MyDerived2> > output;
if(some_computation)
{
output = boost::in_place(MyDerived1(parameters depending of
computation));
}
else
{
other computation;
output = boost::in_place(MyDerived2(other parameters depending of
other computation));
}
MyInterface& blah = boost::apply_visitor(get_base<MyInterface>(),
*output);
blah.execute();
--
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