On Fri, Jul 26, 2024 at 02:42:36PM +0000, Benno Lossin wrote:
> On 26.07.24 16:26, Boqun Feng wrote:
> > On Fri, Jul 26, 2024 at 01:43:38PM +0000, Benno Lossin wrote:
> > [...]
> >>>>
> >>>> You can always get a `&T` from `ARef<T>`, since it implements `Deref`.
> >>>>
> >>>
> >>> Yeah, but this is unrelated. I was talking about that API providers can
> >>> decide whether they want to only provide a `raw_ptr` -> `ARef<Self>` if
> >>> they don't need to provide a `raw_ptr` -> `&Self`.
> >>>
> >>>>> Overall, I feel like we don't necessarily make a preference between
> >>>>> `->&Self` and `->ARef<Self>` functions here, since it's up to the users'
> >>>>> design?
> >>>>
> >>>> I would argue that there should be a clear preference for functions
> >>>> returning `&Self` when possible (ie there is a parameter that the
> >>>
> >>> If "possible" also means there's going to be `raw_ptr` -> `&Self`
> >>> function (as the same publicity level) anyway, then agreed. In other
> >>> words, if the users only need the `raw_ptr` -> `ARef<Self>`
> >>> functionality, we don't want to force people to provide a `raw_ptr` ->
> >>> `&Self` just because, right?
> >>
> >> I see... I am having a hard time coming up with an example where users
> >> would exclusively want `ARef<Self>` though... What do you have in mind?
> >> Normally types wrapped by `ARef` have `&self` methods.
> >>
> >
> > Having `&self` methods doesn't mean the necessarity of a `raw_ptr` ->
> > `&Self` function, for example, a `Foo` is wrapped as follow:
> >
> > struct Foo(Opaque<foo>);
> > impl Foo {
> > pub fn bar(&self) -> Bar { ... }
> > pub unsafe fn get_foo(ptr: *mut foo) -> ARef<Foo> { ... }
> > }
> >
> > in this case, the abstration provider may not want user to get a
> > `raw_ptr` -> `&Self` function, so no need to have it.
>
> I don't understand this, why would the abstraction provider do that? The
Because no user really needs to convert a `raw_ptr` to a `&Self` whose
lifetime is limited to a scope?
Why do we provide a function if no one needs and the solely purpose is
to just avoid providing another function?
> user can already get a `&Foo` reference, so what's the harm having a
> function supplying that directly?
Getting a `&Foo` from a `ARef<Foo>` is totally different than getting a
`&Foo` from a pointer, right? And it's OK for an abstraction provider to
want to avoid that.
Another example that you may not want to provide a `-> &Self` function
is:
struct Foo(Opaque<foo>);
impl Foo {
pub fn bar(&self) -> Bar { ... }
pub fn find_foo(idx: u32) -> ARef<Foo> { ... }
}
in other words, you have a query function (idx -> *mut foo), and I think
in this case, you would avoid `find_foo(idx: u32) -> &Foo`, right?
Honestly, this discussion has been going to a rabit hole. I will mention
and already mentioned the conversion `&Self` -> `ARef<Self>`. Leaving
the preference part blank is fine to me, since if it's a good practice,
then everybody will follow, otherwise, we are missing something here.
Just trying to not make a descision for the users...
Regards,
Boqun
> I get the argument that you need to always convert to `ARef` if users
> only use that, but when `Foo` provides `&self` methods, you're not
> required to have an `ARef`.
>
> ---
> Cheers,
> Benno
>
