On Thursday, April 21, 2016 at 4:33:40 PM UTC+10, Nicholas Nethercote wrote:
> On Thu, Apr 21, 2016 at 4:19 PM, Xidorn Quan <quanx...@gmail.com> wrote:
> >>
> >> Maybe you're referring to factory methods, like this:
> >>
> >> static T* T::New();
> >>
> >> which would return null on failure. Such methods can be useful, but
> >> there's two problems. First, they're not applicable to stack-allocated
> >> objects. Second, you still have to do your fallible initialization
> >> *within* the factory method, and so you still have to choose with
> >> either constructor+Init or constructor+outparam, so you still have to
> >> make a choice.
> >
> > You can probably merge Init into this factory method, and make constructors
> > private.
>
> Inlining Init into the factory method doesn't change the fundamentals.
> Initialization is still split across two functions. You still can't
> use references and |const| as much.
>
> > For stack-allocated objects, you can probably return a Maybe<>?
>
> I played around with Maybe<> and couldn't come up with something nice.
> I may have missed something. Even if there is a nice way involving
> Maybe<>, I'm pretty sure you'll still end up having to make a choice
> between constructor+Init and constructor+outparam within the factory
> method.
>
> Nick
How about another generic helper, e.g.:
template <typename T, typename ...Args>
Maybe<T> MakeCheckedMaybe(Args&&... aArgs)
{
nsresult rv;
Maybe<T> m = Some(T(std::forward<Args>(aArgs)..., &rv));
if (NS_SUCCEEDED(rv)) {
return m;
}
return Nothing();
}
No need for factory methods. ;-)
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